[compiler-rt] [llvm] Reland check-builtins target for LLVM_ENABLE_RUNTIMES (PR #171941)

[Andrew Haberlandt via llvm-commits]

ndrewh wrote:

In addition to the above two, there is also https://lab.llvm.org/buildbot/#/builders/139/builds/25097 which fails with

```
CMake Error at /home/b/sanitizer-x86_64-linux-qemu/build/llvm-project/compiler-rt/test/builtins/CMakeLists.txt:104 (message):
  Target clang_rt.builtins does not exist
```

I think #174443 is the fix for that.

https://github.com/llvm/llvm-project/pull/171941