Make compiler-rt tests work with relocatable SDKs on OS X

Reviewed at http://reviews.llvm.org/D4047



git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@217523 91177308-0d34-0410-b5e6-96231b3b80d8
Merge branch 'master', remote-tracking branch 'trunk/master'