Firefox requires GCC 5.0+ now, but ASAN builds appear to use GCC 4.9 and Clang+libGCC4.8. Can we update our versions? In particular, GCC <4.9 doesn't support the <regex> STL prims.
Duplicating in that direction because the other bug has more actionable information.
(fwiw it's not libgcc that matters, but libstdc++)