[compiler-rt] [sanitizer_common][test-only] Specify full path for sort executable in popen.cpp (PR #171622)

[Aiden Grossman via llvm-commits]

https://github.com/boomanaiden154 commented:

I would expect portability problems with this. I believe there are systems (especially Linux) that put system binaries in places other than `/usr/bin`.

https://github.com/llvm/llvm-project/pull/171622