[clang] [clang] Fix x86_64-windows-msvc over- and under-alignment (PR #196505)

[Hans Wennborg via cfe-commits]

zmodem wrote:

I sent the `c-strings.c` test update separately as https://github.com/llvm/llvm-project/pull/196501

I wasn't sure where to put the shared alignment increase code, and ended up with Microsoft64BitMinGlobalAlign() in TargetInfo.h. Suggestions welcome if there's a better place for it.

This fixes two issues, and would be straight-forward to split into separate PRs if you think that would be better.

Please take a look.

https://github.com/llvm/llvm-project/pull/196505