[libunwind] [libunwind] Compile the asm as well as the C++ source (PR #86351)

[Jon Chesterfield via cfe-commits]

JonChesterfield wrote:

I'm sorry to hear that. I've only used the ENABLE_RUNTIMES in the context of compiling clang first, and then compiling the libraries under runtime with that clang. The recursive invocation drops (most) arguments passed to cmake which has been obstructive in the past.

With standalone build (presumably ENABLE_PROJECTS) removed, how does one build the libraries using an existing compiler?

https://github.com/llvm/llvm-project/pull/86351