[compiler-rt] [llvm] [compiler-rt] Add check-builtins target for LLVM_ENABLE_RUNTIMES builds (PR #166837)

[Wael Yehia via llvm-commits]

w2yehia wrote:

Hi @ndrewh thanks for working on this. I checked the PowerPC linux bots and didn't see this PR's effect, so @daltenty helped debug it for me and we posted a fix in #171741 (essentially you missed a rename).

https://github.com/llvm/llvm-project/pull/166837