[clang] [clang] Handle tm mangling on Solaris in PPMacroExpansion.cpp (PR #100724)

[Rainer Orth via cfe-commits]

rorth wrote:

> > Whatever the case, we need at least a short-term solution now: the Solaris buildbots have been broken for two days now.
> 
> Agreed that we need something in the short term, I'm just trying to find the cleanest "something" under the assumption that this hack will live for a long time. That's why I was hoping we could shove this into CMake somewhere (it's less in everyone's face than the current approach). If we can't do that, then I can live with this approach.

I just don't see how this can be done.  And TBH rather than pile hack upon hack, I'd rather spend some time on duplicating what GCC already does in Clang.  This will require tons and tons of guidance, though.

> Note: precommit CI failures look unrelated.

I think so: I've seen the same failure in my Linux/x86_64 but not on Solaris.

https://github.com/llvm/llvm-project/pull/100724