[libcxx-commits] [libcxxabi] [libc++abi] Improve error message when libunwind is missing from LLVM_ENABLE_RUNTIMES (PR #77991)

[Louis Dionne via libcxx-commits]

ldionne wrote:

The only two bots I still see failing are:
[clang-ppc64le-rhel](https://lab.llvm.org/buildbot/#/builders/57)
[bolt-aarch64-ubuntu-clang](https://lab.llvm.org/buildbot/#/builders/276)

I already fixed the first one on llvm-zorg, and I can't find where the second one is defined, but the bot owner is aware of the problem. @vitalybuka Is there still a need to revert this?

https://github.com/llvm/llvm-project/pull/77991