[clang] [MS] Put dllexported inline global initializers in a comdat (PR #107154)

[Eli Friedman via cfe-commits]

efriedma-quic wrote:

What's the interaction here with the standard's ordering guarantees?  The comment in the code indicates that we can't make a separate comdat for ordered initialization... but inline variables do require partial ordering.  Please update the comment as appropriate.

https://github.com/llvm/llvm-project/pull/107154