Remove redundant MSVC_Z7_OVERRIDE processing and combine "/EHa" flag setup (#23455)
Summary:
- MSVC_Z7_OVERRIDE has already handled in CMakeLists.txt. No need to process it for once more in the Python scripts.
- Option MSVC_Z7_OVERRIDE should be visible to the user only if MSVC is used.
- Move the setting of "/EHa" flag to CMakeLists.txt, where other MSVC-specific flags are processed. This also further prepares the removal of redundant cflags setup in Python build scripts.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/23455
Differential Revision: D16542274
Pulled By: ezyang
fbshipit-source-id: 4d3b8b07161478bbba8a21feb6ea24c9024e21ac
