[sanitizer-coverage] make sure that calls to __sanitizer_cov_trace_pc are not...

[sanitizer-coverage] make sure that calls to __sanitizer_cov_trace_pc are not merged (otherwise different calls get the same PC and confuse fuzzers)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@275449 91177308-0d34-0410-b5e6-96231b3b80d8