[llvm] [BOLT] Enable cross compilation of runtime libraries (PR #101180)

[Peter Waller via llvm-commits]

https://github.com/peterwaller-arm commented:

Thanks for the update; here are some more comments.

Please could you update the pull request body/commit to illustrate how you're moving the runtime libraries so that it's clear to anyone who sees this? i.e. Just put `lib/libbolt_rt_instr.a -> lib/Target/<target>/libbolt_rt_instr.a` there.

Speaking of which, I wonder if `lib/<target>/<lib>` would be sufficient (perhaps having `/Target/` is redundant?

https://github.com/llvm/llvm-project/pull/101180