[gcc] Allow GCC insert .cfi_startproc and .cfi_endproc.

NaCl GAS supports these assembler directives. Though on Mac buildbots this
capability is not recognized due to the lack of readelf installed. Supporting
these directives is essential to have correct backtraces listed with valgrind.

BUG: http://code.google.com/p/nativeclient/issues/detail?id=663

Review URL: http://codereview.chromium.org/2805058
1 file changed