[sanitizer-common] Fixing the ASan test build failure on OS X

The change in r224819 started using internal_unlink in a sanitizer_common unit test. For some reason, internal_unlink is not defined in sanitizer_mac.cc, fixing that.



git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@224910 91177308-0d34-0410-b5e6-96231b3b80d8