[llvm] [runtimes] Skip linker validation in per-target runtime sub-builds (PR #189933)

[Joseph Huber via llvm-commits]

https://github.com/jhuber6 approved this pull request.

I've had similar issues with the NVPTX toolchain. It's reasonable to be conservative here, because a lot of this LLVM is trying to set up a toolchain to build LLVM while most of the runtimes are pretty much freestanding.

I think this is fine, but I'd like some other opinions.

https://github.com/llvm/llvm-project/pull/189933