How to run tests for compiler-rt?

As the question says, how do I run tests for compiler-rt? I’m attempting to add a new builtin function but cannot figure out how to run the test file I added.

check-compiler-rt and check-builtins appear as unknown targets when I try building with ninja. I also tried running bin/llvm-lit -vv /path/to/my/test but run into an AttributeError in the python script attempting to run it.

I have compiler-rt as one of my enabled projects and -DCOMPILER_RT_INCLUDE_TESTS=On in my cmake invocation. Is there anything else I’m missing?

Thanks,
Leonard