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

[Andrew Haberlandt via llvm-commits]

ndrewh wrote:

>  I would think there would be postcommit coverage of most of the common configurations, but I'm not sure.

There wouldn't be unless one of the bots does a standalone compiler-rt / builtins build.

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