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

[Alexander Richardson via llvm-commits]

arichardson wrote:

> Any idea if there is a possibility/risk that this patch introduces some race condition so some files might be used before they're installed?
> 
> The reason I'm asking is that we now sometimes see errors like compiler-rt/lib/fuzzer/FuzzerExtraCountersWindows.cpp:12:10: fatal error: 'cstdint' file not found

There shouldn't be, but I'll take a look if there are some missing dependencies.

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