Thanks, I really appreciate your commitment for this! So I’ve run this by Ninja, and it exited pretty fast. The error log is quite long:
-- The CXX compiler identification is GNU 7.2.0
-- The C compiler identification is GNU 7.2.0
-- Check for working CXX compiler: C:/Program Files/Haskell Platform/8.4.3/mingw/bin/c++.exe
-- Check for working CXX compiler: C:/Program Files/Haskell Platform/8.4.3/mingw/bin/c++.exe -- broken
CMake Error at C:/Users/MarcinM/AppData/Local/Programs/Python/Python36/Lib/site-packages/cmake/data/share/cmake-3.13/Modules/CMakeTestCXXCompiler.cmake:45 (message):
  The C++ compiler

    "C:/Program Files/Haskell Platform/8.4.3/mingw/bin/c++.exe"

  is not able to compile a simple test program.

  It fails with the following output:

    Change Dir: C:/Users/MarcinM/pytorch/build/CMakeFiles/CMakeTmp

    Run Build Command:"C:/Users/MarcinM/AppData/Local/Programs/Python/Python36/Scripts/ninja.exe" "cmTC_42959"
    [1/2] Building CXX object CMakeFiles/cmTC_42959.dir/testCXXCompiler.cxx.obj
    FAILED: CMakeFiles/cmTC_42959.dir/testCXXCompiler.cxx.obj
    C:\PROGRA~1\HASKEL~1\847A5C~1.3\mingw\bin\C__~1.EXE    /EHa -o CMakeFiles/cmTC_42959.dir/testCXXCompiler.cxx.obj -c testCXXCompiler.cxx
    C__~1.EXE: error: /EHa: No such file or directory
    ninja: build stopped: subcommand failed.




  CMake will not be able to correctly generate this project.
Call Stack (most recent call first):
  CMakeLists.txt:11 (project)


-- Configuring incomplete, errors occurred!
See also "C:/Users/MarcinM/pytorch/build/CMakeFiles/CMakeOutput.log".
See also "C:/Users/MarcinM/pytorch/build/CMakeFiles/CMakeError.log".
Traceback (most recent call last):
  File "setup.py", line 710, in <module>
    build_deps()
  File "setup.py", line 282, in build_deps
    build_dir='build')
  File "C:\Users\MarcinM\pytorch\tools\build_pytorch_libs.py", line 253, in build_caffe2
    my_env)
  File "C:\Users\MarcinM\pytorch\tools\build_pytorch_libs.py", line 233, in run_cmake
    check_call(cmake_args, cwd=build_dir, env=my_env)
  File "C:\Users\MarcinM\AppData\Local\Programs\Python\Python36\lib\subprocess.py", line 291, in check_call
    raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command '['cmake', '-GNinja', '-DBUILDING_WITH_TORCH_LIBS=ON', '-DBUILD_BINARY=False', '-DBUILD_CAFFE2_OPS=True', '-DBUILD_PYTHON=True', '-DBUILD_SHARED_LIBS=ON', '-DBUILD_TEST=True', '-DBUILD_TORCH=ON', '-DCAFFE2_STATIC_LINK_CUDA=False', '-DCMAKE_BUILD_TYPE=Release', '-DCMAKE_CXX_FLAGS=  /EHa', '-DCMAKE_C_FLAGS=  /EHa', '-DCMAKE_EXE_LINKER_FLAGS=', '-DCMAKE_INSTALL_PREFIX=C:\\Users\\MarcinM\\pytorch/torch', '-DCMAKE_PREFIX_PATH=C:\\Users\\MarcinM\\AppData\\Local\\Programs\\Python\\Python36\\Lib\\site-packages', '-DCMAKE_SHARED_LINKER_FLAGS=', '-DINSTALL_TEST=True', '-DNCCL_EXTERNAL=False', '-DNUMPY_INCLUDE_DIR=C:/Users/MarcinM/AppData/Local/Programs/Python/Python36/lib/site-packages/numpy/core/include', '-DONNX_ML=False', '-DONNX_NAMESPACE=onnx_torch', '-DPYTHON_EXECUTABLE=C:/Users/MarcinM/AppData/Local/Programs/Python/Python36/python.exe', '-DPYTHON_INCLUDE_DIR=C:/Users/MarcinM/AppData/Local/Programs/Python/Python36/include', '-DPYTHON_LIBRARY=C:/Users/MarcinM/AppData/Local/Programs/Python/Python36/libs/python36.lib', '-DTHD_SO_VERSION=1', '-DTORCH_BUILD_VERSION=1.1.0a0+e5cdd94', '-DUSE_CUDA=True', '-DUSE_DISTRIBUTED=False', '-DUSE_FBGEMM=True', '-DUSE_FFMPEG=False', '-DUSE_LEVELDB=False', '-DUSE_LMDB=False', '-DUSE_MKLDNN=True', '-DUSE_NCCL=False', '-DUSE_NNPACK=True', '-DUSE_NUMPY=True', '-DUSE_OPENCV=False', '-DUSE_QNNPACK=True', '-DUSE_ROCM=False', '-DUSE_SYSTEM_EIGEN_INSTALL=OFF', '-DUSE_SYSTEM_NCCL=False', '-DUSE_TENSORRT=False', '-DMKLDNN_ENABLE_CONCURRENT_EXEC=ON', 'C:\\Users\\MarcinM\\pytorch']' returned non-zero exit status 1.

The folder C:/Users/MarcinM/pytorch/build/CMakeFiles/CMakeTmp is empty if this is any help. Also the c++.exe file is present in C:\Program Files\Haskell Platform\8.4.3\mingw\bin.