[compiler-rt] [compiler-rt] Use installed libc++(abi) for tests instead of build tree (PR #115077)

[Alexander Richardson via llvm-commits]

arichardson wrote:

Sounds like I need to override the install command to clear DESTDIR: https://gitlab.kitware.com/cmake/cmake/-/issues/18165

https://github.com/llvm/llvm-project/pull/115077