[sanitizer_common] Add suffix to lit testsuite name to distinguish subtargets.

Summary:
This fixes duplicate test names in the test results, so:
  PASS: SanitizerCommon-asan :: fopen_nullptr.c (304 of 431)
  PASS: SanitizerCommon-asan :: fopen_nullptr.c (305 of 431)
is now:
  PASS: SanitizerCommon-asan-i386-Linux :: fopen_nullptr.c (282 of 431)             
  PASS: SanitizerCommon-asan-x86_64-Linux :: fopen_nullptr.c (316 of 431)

Reviewers: samsonov

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D16850

llvm-svn: 260227