[Bug sanitizer/63559] -fsanitize=thread sets no preprocessor flags

[dvyukov at google dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63559

--- Comment #3 from Dmitry Vyukov <dvyukov at google dot com> ---
Ah, OK, thanks.

FWIW, TBB is open-source. However it uses hand-rolled atomic operations, so
tsan won't work out-of-the box anyway.