[clang] [llvm] [X86] Add WinCall Calling Convention and x86_64apx-windows(-gnu/-msvc) triplets (PR #215585)

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void2012 wrote:

Does x86 (32-bit) have a similar problem? I recall things like `std::string_view` weren't optimized properly due to the calling convention, too.

https://github.com/llvm/llvm-project/pull/215585