update build_host_protoc command for macos cross compilation (#50922)
Summary:
Currently, adding a cross compile build is failing on CI due to a cmake builtin compiler check that does not pass due to cross compiling the host protoc library.
Setting the CMAKE_TRY_COMPILE_TARGET_TYPE flag should fix it. (Based on this [SOF answer](https://stackoverflow.com/questions/53633705/cmake-the-c-compiler-is-not-able-to-compile-a-simple-test-program).)
To test that this works, please run: `CMAKE_OSX_ARCHITECTURES=arm64 USE_MKLDNN=OFF USE_NNPACK=OFF USE_QNNPACK=OFF USE_PYTORCH_QNNPACK=OFF BUILD_TEST=OFF python setup.py install` from a Mac x86_64 machine with Xcode12.3 (anything with MacOS 11 SDK).
Then, you can check that things were compiled for arm by running `lipo -info <file>` for any file in the `build/lib` directory.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/50922
Reviewed By: malfet
Differential Revision: D26355054
Pulled By: janeyx99
fbshipit-source-id: 919f3f9bd95d7c7bba6ab3a95428d3ca309f8ead
