[clang] [llvm] [llvm] Add support for building on illumos (PR #74930)

[Fangrui Song via cfe-commits]

MaskRay wrote:

> illumos has an older version of the Solaris linker that does not support the GNU version script compat nor version scripts and does not support -Bsymbolic-functions. Treat illumos linker separately.

Are they aware of the issue and is there a tracking feature request/issue? It seems that this patch adds code to hard code the implementation properties which may become stale.

https://github.com/llvm/llvm-project/pull/74930