I am trying to build PyTorch 1.9.0 from source on a POWER8 machine with CUDA 11.5 and Python 3.8 compatibility. As far as I understand there are no binaries/build configurations for this setup so I have been trying to find a workaround. My approach is to follow the same guidelines as in the From Source section on the Pytorch repository, except I run git checkout tags/v1.9.0 prior to syncing/updating the submodules. Then I create a conda environment and run:
$ conda install numpy ninja pyyaml setuptools cmake cffi typing_extensions future six requests dataclasses

Note that I do not install mkl as I am building on a ppc64le architecture. I then have to separately install magma via the compass channel, which has a CUDA 11.2 compatible version. Then I export the following environment variables:
export PATH=/usr/local/cuda-11.5/bin:$PATH
export LD_LIBRARY_PATH=/usr/local/cuda-11.5/lib64:$LD_LIBRARY_PATH
export CC=/usr/bin/gcc
export CXX=/usr/bin/g++
export USE_CUDA="True"

If I try to run the setup.py script at this point I get multiple errors about cub namespace bugs and conflicts with thrust, which seem to be addressed in later commits. To address these I followed the updates made in this commit, namely by creating the caffe2/utils/cub_namespace.cuh script and adjusting the include statements within the relevant caffe2 scripts, as well as adjusting the cmake/Dependencies.cmake.
After updating the git submodules, I run the setup script:
export CMAKE_PREFIX_PATH=${CONDA_PREFIX:-"$(dirname $(which conda))/../"} 
BUILD_TEST=0 USE_SYSTEM_NCCL=1 python setup.py install

This appears to address the aforementioned issues and the build almost completes but around step 3080/3100 I get the following error:
FAILED: bin/torch_shm_manager 
: && /usr/bin/g++ -Wno-deprecated -fvisibility-inlines-hidden -fopenmp -DNDEBUG -DUSE_KINETO -DLIBKINETO_NOCUPTI -DSYMBOLICATE_MOBILE_DEBUG_HANDLE -O2 -fPIC -Wno-narrowing -Wall -Wextra -Werror=return-type -Wno-missing-field-initializers -Wno-type-limits -Wno-array-bounds -Wno-unknown-pragmas -Wno-sign-compare -Wno-unused-parameter -Wno-unused-variable -Wno-unused-function -Wno-unused-result -Wno-unused-local-typedefs -Wno-strict-overflow -Wno-strict-aliasing -Wno-error=deprecated-declarations -Wno-stringop-overflow -Wno-psabi -Wno-error=pedantic -Wno-error=redundant-decls -Wno-error=old-style-cast -fdiagnostics-color=always -faligned-new -Wno-unused-but-set-variable -Wno-maybe-uninitialized -fno-math-errno -fno-trapping-math -Werror=format -Werror=cast-function-type -Wno-stringop-overflow -DHAVE_VSX_CPU_DEFINITION -O3 -DNDEBUG -DNDEBUG -rdynamic    -rdynamic caffe2/torch/lib/libshm/CMakeFiles/torch_shm_manager.dir/manager.cpp.o -o bin/torch_shm_manager  -Wl,-rpath,/home/mac/pytorch/build/lib:/home/mac/miniconda3/envs/aml_env/lib:/usr/local/cuda-11.5/lib64:/usr/local/cuda-11.5/lib:  lib/libshm.so  -lrt  lib/libtorch.so  -Wl,--no-as-needed,"/home/mac/pytorch/build/lib/libtorch_cpu.so" -Wl,--as-needed  lib/libprotobuf.a  -pthread  -Wl,--no-as-needed,"/home/mac/pytorch/build/lib/libtorch_cuda.so" -Wl,--as-needed  lib/libc10_cuda.so  /usr/local/cuda-11.5/lib64/libcudart.so  /home/mac/miniconda3/envs/aml_env/lib/libnvToolsExt.so  /usr/local/cuda-11.5/lib64/libcufft.so  /usr/local/cuda-11.5/lib64/libcurand.so  /usr/local/cuda-11.5/lib64/libcublas.so  /usr/local/cuda-11.5/lib/libcudnn.so  lib/libc10.so && :
/usr/local/cuda-11.5/lib64/libcublas.so: undefined reference to `cublasLtGetStatusString@libcublasLt.so.11'
/usr/local/cuda-11.5/lib64/libcublas.so: undefined reference to `cublasLtGetStatusName@libcublasLt.so.11'
collect2: error: ld returned 1 exit status
[3084/3110] Building CXX object caffe2/torch/CMakeFiles/torch_python.dir/csrc/autograd/generated/python_torch_functions.cpp.o
[3085/3110] Building NVCC (Device) object modules/detectron/CMakeFiles/caffe2_detectron_ops_gpu.dir/caffe2_detectron_ops_gpu_generated_group_spatial_softmax_op.cu.o
[3086/3110] Building NVCC (Device) object modules/detectron/CMakeFiles/caffe2_detectron_ops_gpu.dir/caffe2_detectron_ops_gpu_generated_smooth_l1_loss_op.cu.o
[3087/3110] Building NVCC (Device) object modules/detectron/CMakeFiles/caffe2_detectron_ops_gpu.dir/caffe2_detectron_ops_gpu_generated_ps_roi_pool_op.cu.o
[3088/3110] Building NVCC (Device) object modules/detectron/CMakeFiles/caffe2_detectron_ops_gpu.dir/caffe2_detectron_ops_gpu_generated_upsample_nearest_op.cu.o
[3089/3110] Building NVCC (Device) object modules/detectron/CMakeFiles/caffe2_detectron_ops_gpu.dir/caffe2_detectron_ops_gpu_generated_sigmoid_focal_loss_op.cu.o
[3090/3110] Building NVCC (Device) object modules/detectron/CMakeFiles/caffe2_detectron_ops_gpu.dir/caffe2_detectron_ops_gpu_generated_select_smooth_l1_loss_op.cu.o
[3091/3110] Building NVCC (Device) object modules/detectron/CMakeFiles/caffe2_detectron_ops_gpu.dir/caffe2_detectron_ops_gpu_generated_sample_as_op.cu.o
[3092/3110] Building NVCC (Device) object modules/detectron/CMakeFiles/caffe2_detectron_ops_gpu.dir/caffe2_detectron_ops_gpu_generated_roi_pool_f_op.cu.o
[3093/3110] Building NVCC (Device) object modules/detectron/CMakeFiles/caffe2_detectron_ops_gpu.dir/caffe2_detectron_ops_gpu_generated_spatial_narrow_as_op.cu.o
[3094/3110] Building NVCC (Device) object modules/detectron/CMakeFiles/caffe2_detectron_ops_gpu.dir/caffe2_detectron_ops_gpu_generated_softmax_focal_loss_op.cu.o
[3095/3110] Building NVCC (Device) object modules/detectron/CMakeFiles/caffe2_detectron_ops_gpu.dir/caffe2_detectron_ops_gpu_generated_sigmoid_cross_entropy_loss_op.cu.o
[3096/3110] Building CXX object caffe2/torch/CMakeFiles/torch_python.dir/csrc/autograd/generated/python_functions.cpp.o
ninja: build stopped: subcommand failed.
Building wheel torch-1.9.0a0+gitd69c22d
-- Building version 1.9.0a0+gitd69c22d
cmake -GNinja -DBUILD_PYTHON=True -DBUILD_TEST=False -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=/home/mac/pytorch/torch -DCMAKE_PREFIX_PATH=/home/mac/miniconda3/envs/aml_env -DNUMPY_INCLUDE_DIR=/home/mac/miniconda3/envs/aml_env/lib/python3.8/site-packages/numpy/core/include -DPYTHON_EXECUTABLE=/home/mac/miniconda3/envs/aml_env/bin/python -DPYTHON_INCLUDE_DIR=/home/mac/miniconda3/envs/aml_env/include/python3.8 -DPYTHON_LIBRARY=/home/mac/miniconda3/envs/aml_env/lib/libpython3.8.so.1.0 -DTORCH_BUILD_VERSION=1.9.0a0+gitd69c22d -DUSE_CUDA=True -DUSE_NUMPY=True -DUSE_SYSTEM_NCCL=1 /home/mac/pytorch
cmake --build . --target install --config Release -- -j 160

Here is an overview of the environment variables and locations/ versions of relevant build tools/ libraries:
-- ******** Summary ********
-- General:
--   CMake version         : 3.19.6
--   CMake command         : /home/mac/miniconda3/envs/aml_env/bin/cmake
--   System                : Linux
--   C++ compiler          : /usr/bin/g++
--   C++ compiler id       : GNU
--   C++ compiler version  : 8.5.0
--   Using ccache if found : ON
--   Found ccache          : CCACHE_PROGRAM-NOTFOUND
--   CXX flags             :  -Wno-deprecated -fvisibility-inlines-hidden -fopenmp -DNDEBUG -DUSE_KINETO -DLIBKINETO_NOCUPTI -DSYMBOLICATE_MOBILE_DEBUG_HANDLE -O2 -fPIC -Wno-narrowing -Wall -Wextra -Werror=return-type -Wno-missing-field-initializers -Wno-type-limits -Wno-array-bounds -Wno-unknown-pragmas -Wno-sign-compare -Wno-unused-parameter -Wno-unused-variable -Wno-unused-function -Wno-unused-result -Wno-unused-local-typedefs -Wno-strict-overflow -Wno-strict-aliasing -Wno-error=deprecated-declarations -Wno-stringop-overflow -Wno-psabi -Wno-error=pedantic -Wno-error=redundant-decls -Wno-error=old-style-cast -fdiagnostics-color=always -faligned-new -Wno-unused-but-set-variable -Wno-maybe-uninitialized -fno-math-errno -fno-trapping-math -Werror=format -Werror=cast-function-type -Wno-stringop-overflow
--   Build type            : Release
--   Compile definitions   : ONNX_ML=1;ONNXIFI_ENABLE_EXT=1;ONNX_NAMESPACE=onnx_torch;MAGMA_V2;HAVE_MMAP=1;_FILE_OFFSET_BITS=64;HAVE_SHM_OPEN=1;HAVE_SHM_UNLINK=1;HAVE_MALLOC_USABLE_SIZE=1;USE_EXTERNAL_MZCRC;MINIZ_DISABLE_ZIP_READER_CRC32_CHECKS
--   CMAKE_PREFIX_PATH     : /home/mac/miniconda3/envs/aml_env;/usr/local/cuda-11.5;/usr/local/cuda-11.5
--   CMAKE_INSTALL_PREFIX  : /home/mac/pytorch/torch
--   USE_GOLD_LINKER       : OFF
-- 
--   TORCH_VERSION         : 1.9.0
--   CAFFE2_VERSION        : 1.9.0
--   BUILD_CAFFE2          : ON
--   BUILD_CAFFE2_OPS      : ON
--   BUILD_CAFFE2_MOBILE   : OFF
--   BUILD_STATIC_RUNTIME_BENCHMARK: OFF
--   BUILD_TENSOREXPR_BENCHMARK: OFF
--   BUILD_BINARY          : OFF
--   BUILD_CUSTOM_PROTOBUF : ON
--     Link local protobuf : ON
--   BUILD_DOCS            : OFF
--   BUILD_PYTHON          : True
--     Python version      : 3.8.12
--     Python executable   : /home/mac/miniconda3/envs/aml_env/bin/python
--     Pythonlibs version  : 3.8.12
--     Python library      : /home/mac/miniconda3/envs/aml_env/lib/libpython3.8.so.1.0
--     Python includes     : /home/mac/miniconda3/envs/aml_env/include/python3.8
--     Python site-packages: lib/python3.8/site-packages
--   BUILD_SHARED_LIBS     : ON
--   CAFFE2_USE_MSVC_STATIC_RUNTIME     : OFF
--   BUILD_TEST            : False
--   BUILD_JNI             : OFF
--   BUILD_MOBILE_AUTOGRAD : OFF
--   BUILD_LITE_INTERPRETER: OFF
--   INTERN_BUILD_MOBILE   : 
--   USE_BLAS              : 1
--     BLAS                : open
--   USE_LAPACK            : 1
--     LAPACK              : open
--   USE_ASAN              : OFF
--   USE_CPP_CODE_COVERAGE : OFF
--   USE_CUDA              : True
--     Split CUDA          : OFF
--     CUDA static link    : OFF
--     USE_CUDNN           : ON
--     CUDA version        : 11.5
--     cuDNN version       : 8.3.1
--     CUDA root directory : /usr/local/cuda-11.5
--     CUDA library        : /usr/local/cuda-11.5/lib64/stubs/libcuda.so
--     cudart library      : /usr/local/cuda-11.5/lib64/libcudart.so
--     cublas library      : /usr/local/cuda-11.5/lib64/libcublas.so
--     cufft library       : /usr/local/cuda-11.5/lib64/libcufft.so
--     curand library      : /usr/local/cuda-11.5/lib64/libcurand.so
--     cuDNN library       : /usr/local/cuda-11.5/lib/libcudnn.so
--     nvrtc               : /home/mac/miniconda3/envs/aml_env/lib/libnvrtc.so
--     CUDA include path   : /usr/local/cuda-11.5/include
--     NVCC executable     : /usr/local/cuda-11.5/bin/nvcc
--     NVCC flags          : -Xfatbin;-compress-all;-DONNX_NAMESPACE=onnx_torch;-gencode;arch=compute_60,code=sm_60;-Xcudafe;--diag_suppress=cc_clobber_ignored,--diag_suppress=integer_sign_change,--diag_suppress=useless_using_declaration,--diag_suppress=set_but_not_used,--diag_suppress=field_without_dll_interface,--diag_suppress=base_class_has_different_dll_interface,--diag_suppress=dll_interface_conflict_none_assumed,--diag_suppress=dll_interface_conflict_dllexport_assumed,--diag_suppress=implicit_return_from_non_void_function,--diag_suppress=unsigned_compare_with_zero,--diag_suppress=declared_but_not_referenced,--diag_suppress=bad_friend_decl;-std=c++14;-Xcompiler;-fPIC;--expt-relaxed-constexpr;--expt-extended-lambda -Wno-deprecated-gpu-targets --expt-extended-lambda -DCUB_WRAPPED_NAMESPACE=at_cuda_detail -DCUDA_HAS_FP16=1 -D__CUDA_NO_HALF_OPERATORS__ -D__CUDA_NO_HALF_CONVERSIONS__ -D__CUDA_NO_HALF2_OPERATORS__ -D__CUDA_NO_BFLOAT16_CONVERSIONS__;-Xcompiler;-fPIC
--     CUDA host compiler  : /usr/bin/gcc
--     NVCC --device-c     : OFF
--     USE_TENSORRT        : OFF
--   USE_ROCM              : OFF
--   USE_EIGEN_FOR_BLAS    : ON
--   USE_FBGEMM            : OFF
--     USE_FAKELOWP          : OFF
--   USE_KINETO            : ON
--   USE_FFMPEG            : OFF
--   USE_GFLAGS            : OFF
--   USE_GLOG              : OFF
--   USE_LEVELDB           : OFF
--   USE_LITE_PROTO        : OFF
--   USE_LMDB              : OFF
--   USE_METAL             : OFF
--   USE_PYTORCH_METAL     : OFF
--   USE_FFTW              : OFF
--   USE_MKL               : OFF
--   USE_MKLDNN            : OFF
--   USE_NCCL              : ON
--     USE_SYSTEM_NCCL     : 1
--   USE_NNPACK            : OFF
--   USE_NUMPY             : ON
--   USE_OBSERVERS         : ON
--   USE_OPENCL            : OFF
--   USE_OPENCV            : OFF
--   USE_OPENMP            : ON
--   USE_TBB               : OFF
--   USE_VULKAN            : OFF
--   USE_PROF              : OFF
--   USE_QNNPACK           : OFF
--   USE_PYTORCH_QNNPACK   : OFF
--   USE_REDIS             : OFF
--   USE_ROCKSDB           : OFF
--   USE_ZMQ               : OFF
--   USE_DISTRIBUTED       : ON
--     USE_MPI             : OFF
--     USE_GLOO            : ON
--     USE_TENSORPIPE      : ON
--   USE_DEPLOY           : OFF
--   Public Dependencies  : Threads::Threads
--   Private Dependencies : cpuinfo;fp16;gloo;tensorpipe;aten_op_header_gen;foxi_loader;rt;fmt::fmt-header-only;kineto;gcc_s;gcc;dl

Any idea on what the problem could be? Thanks in advance!