[compiler-rt] Remove unwanted --check-prefix=CHECK from unit tests. NFC.

Summary:
Removed unwanted --check-prefix=CHECK from the following unit tests:
      test/asan/TestCases/Posix/start-deactivated.cc
      test/tsan/Darwin/ignored-interceptors.mm

 Patch by: Mandeep Singh Grang (mgrang)

Reviewers: samsonov, kcc, dvyukov, eugenis

Differential Revision: http://reviews.llvm.org/D19281

llvm-svn: 266813