Hi everyone.
I’m in the process of converting our models from Python to C++ for production. For that it seems we need to build Pytorch from source as the prebuilt libtorch doesnt come with torch.h headers and alike !
I’m on Windows 10 1803 and  have Visual Studio 2019 installed (v16.6.3). I dont have any GPUs so I didnt install CUDA! or NVTX.
I have anaconda and python 3.7 installed and all the deps are installed using the following command:
conda install numpy ninja pyyaml mkl mkl-include setuptools cmake cffi

I cloned Pytorch as stated in the readme :
git clone --recursive https://github.com/pytorch/pytorch
cd pytorch
# if you are updating an existing checkout
git submodule sync
git submodule update --init --recursive

But upon executing these commands :
:: [Optional] If you want to build with VS 2019 generator, please change the value in the next line to `Visual Studio 16 2019`.
:: Note: This value is useless if Ninja is detected. However, you can force that by using `set USE_NINJA=OFF`.
set CMAKE_GENERATOR=Visual Studio 16 2019

:: Read the content in the previous section carefully before you proceed.
:: [Optional] If you want to override the underlying toolset used by Ninja and Visual Studio with CUDA, please run the following script block.
:: "Visual Studio 2017 Developer Command Prompt" will be run automatically.
:: Make sure you have CMake >= 3.12 before you do this when you use the Visual Studio generator.
set CMAKE_GENERATOR_TOOLSET_VERSION=14.11
set DISTUTILS_USE_SDK=1
for /f "usebackq tokens=*" %i in (`"%ProgramFiles(x86)%\Microsoft Visual Studio\Installer\vswhere.exe" -version [15^,16^) -products * -latest -property installationPath`) do call "%i\VC\Auxiliary\Build\vcvarsall.bat" x64 -vcvars_ver=%CMAKE_GENERATOR_TOOLSET_VERSION%

:: [Optional] If you want to override the cuda host compiler
set CUDAHOSTCXX=C:\Program Files (x86)\Microsoft Visual Studio\2017\Enterprise\VC\Tools\MSVC\14.11.25503\bin\HostX64\x64\cl.exe

python setup.py install

I face these errors:
D:\Codes\pytorch>python setup.py install
Building wheel torch-1.7.0a0+8376284
-- Building version 1.7.0a0+8376284
cmake -GNinja -DBUILD_PYTHON=True -DBUILD_TEST=True -DCMAKE_BUILD_TYPE=Release -DCMAKE_GENERATOR=Visual Studio 16 2019 -DCMAKE_GENERATOR_TOOLSET_VERSION=14.11 -DCMAKE_INSTALL_PREFIX=D:\Codes\pytorch\torch -DCMAKE_PREFIX_PATH=C:\Users\User\Anaconda3\Lib\site-packages -DNUMPY_INCLUDE_DIR=C:\Users\User\Anaconda3\Lib\site-packages\numpy\core\include -DPYTHON_EXECUTABLE=C:\Users\User\Anaconda3\python.exe -DPYTHON_INCLUDE_DIR=C:\Users\User\Anaconda3\include -DPYTHON_LIBRARY=C:\Users\User\Anaconda3/libs/python37.lib -DTORCH_BUILD_VERSION=1.7.0a0+8376284 -DUSE_NUMPY=True D:\Codes\pytorch
CMake Error: Error: generator : Ninja
Does not match the generator used previously: Visual Studio 16 2019
Either remove the CMakeCache.txt file and CMakeFiles directory or choose a different binary directory.
Traceback (most recent call last):
  File "setup.py", line 737, in <module>
    build_deps()
  File "setup.py", line 321, in build_deps
    cmake=cmake)
  File "D:\Codes\pytorch\tools\build_pytorch_libs.py", line 59, in build_caffe2
    rerun_cmake)
  File "D:\Codes\pytorch\tools\setup_helpers\cmake.py", line 329, in generate
    self.run(args, env=my_env)
  File "D:\Codes\pytorch\tools\setup_helpers\cmake.py", line 141, in run
    check_call(command, cwd=self.build_dir, env=env)
  File "C:\Users\User\Anaconda3\Lib\subprocess.py", line 347, in check_call
    raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command '['cmake', '-GNinja', '-DBUILD_PYTHON=True', '-DBUILD_TEST=True', '-DCMAKE_BUILD_TYPE=Release', '-DCMAKE_GENERATOR=Visual Studio 16 2019', '-DCMAKE_GENERATOR_TOOLSET_VERSION=14.11', '-DCMAKE_INSTALL_PREFIX=D:\\Codes\\pytorch\\torch', '-DCMAKE_PREFIX_PATH=C:\\Users\\User\\Anaconda3\\Lib\\site-packages', '-DNUMPY_INCLUDE_DIR=C:\\Users\\User\\Anaconda3\\Lib\\site-packages\\numpy\\core\\include', '-DPYTHON_EXECUTABLE=C:\\Users\\User\\Anaconda3\\python.exe', '-DPYTHON_INCLUDE_DIR=C:\\Users\\User\\Anaconda3\\include', '-DPYTHON_LIBRARY=C:\\Users\\User\\Anaconda3/libs/python37.lib', '-DTORCH_BUILD_VERSION=1.7.0a0+8376284', '-DUSE_NUMPY=True', 'D:\\Codes\\pytorch']' returned non-zero exit status 1.

What am I doing wrong?
Any help is greatly appreciated