[Bug sanitizer/64354] no preprocessor symbol __SANITIZE_THREAD__

[dvyukov at google dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64354

--- Comment #1 from Dmitry Vyukov <dvyukov at google dot com> ---
We've hit this issue while implementing Go support for C++ ThreadSanitizer:
https://github.com/golang/go/issues/14602
__has_feature obviously does not work. Providing __SANITIZE_THREAD__ looks very
reasonable since we provide __SANITIZE_ADDRESS__.