[Bug sanitizer/59148] FAIL: c-c++-common/asan/strncpy-overflow-1.c -O0 execution test on darwin13

[glider at google dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59148

--- Comment #3 from Alexander Potapenko <glider at google dot com> ---
GCC emits calls to __strcpy_chk and __strncpy_chk in this test, which happens
because of source fortification being on by default on Darwin.
In Clang we're passing -D_FORTIFY_SOURCE=0 when compiling with
-fsanitize=address.

I've checked that manually adding -D_FORTIFY_SOURCE=0 fixes
strncpy-overflow-1.c

Jack, can you please make the changes in the GCC driver?