[dsymutil] Suppress CoreFoundation leaks in tests.

This suppresses CoreFoundation originated leaks in the dsymutil tests.
I'm not sure if this is a false positive or not, but either way we don't
have control over it and shouldn't keep the bot red.

http://lab.llvm.org:8080/green/job/clang-stage2-cmake-RgSan/

llvm-svn: 342724