Summary:
In https://github.com/facebook/rocksdb/issues/8539 I accidentally only checked for GCC TSAN, which is
what I tested locally, while CircleCI and FB CI use clang TSAN. Related:
other existing code like in stack_trace.cc only check for clang TSAN.

I've now standardized these to the GCC convention in port/lang.h, so now

    #ifdef __SANITIZE_THREAD__

can check for any TSAN (assuming lang.h include)

Pull Request resolved: https://github.com/facebook/rocksdb/pull/8543

Test Plan:
Put an assert(false) in slice_test and look for the NOTE
about "signal-unsafe call", both GCC and clang. Eventually, CircleCI
TSAN in https://github.com/facebook/rocksdb/issues/8538

Reviewed By: zhichao-cao

Differential Revision: D29728483

Pulled By: pdillinger

fbshipit-source-id: 8a3b8015c2ed48078214c3ee17146a2c3f11c9f7