[llvm] Improve compiler-rt build structure and export compilation info (PR #190088)

[Jordan Rupprecht via llvm-commits]

rupprecht wrote:

> I can look into symbolic macros

I believe there are many downstream users of LLVM bazel that are on bazel 7, and symbolic macros were only added in bazel 8. Maybe it's fine as long as downstream users don't use compiler-rt build rules (and probably they aren't)? Or perhaps symbolic macro support was backported to later versions of bazel 7? (Haven't checked, though I would assume not).

https://github.com/llvm/llvm-project/pull/190088