[libc-commits] [libc] [libc] Fix passing the full runtime target for multilibs (PR #136208)

[Petr Hosek via libc-commits]

petrhosek wrote:

> > > Summary: The multilib builds pass `+name` to the runtime target.
> > 
> > 
> > This shouldn't happen, what's your build configuration?
> 
> ```
>     -DRUNTIMES_x86_64-unknown-linux-gnu_LLVM_ENABLE_RUNTIMES=${RUNTIMES}                           \
>     -DRUNTIMES_x86_64-unknown-linux-gnu+debug_LLVM_ENABLE_RUNTIMES=${RUNTIMES}                           \
>     -DLLVM_RUNTIME_MULTILIBS=debug                                                                 \
>     -DLLVM_RUNTIME_MULTILIB_debug_TARGETS=x86_64-unknown-linux-gnu                                 \
> ```
> 
> Something like this, I couldn't figure out how it expected it to work. If I just tried doing it any other way it would complain that the target didn't exist.

This looks correct but I suspect there might be a bug somewhere in the runtimes implementation since we shouldn't be passing the `+${multilib}` to the subbuild. I'd prefer addressing the issue rather than working around it inside the libc build. Let me reproduce this locally to figure out what's the problem.

https://github.com/llvm/llvm-project/pull/136208