Filter -fstack-protector out of cflags for nacl_helper_bootstrap

Filter -fstack-protector out of cflags for nacl_helper_bootstrap

Some Linux distributions want to build Chromium with
GYP_DEFINES="release_extra_cflags='-mthis -fstack-protector -mthat'".
This breaks the build of nacl_helper_bootstrap because we need to
ensure that -fstack-protector is never used for that file.

Filtering out the potentially incompatible options fixes this scenario.

BUG= http://code.google.com/p/chromium/issues/detail?id=104569
TEST= manually tested in chromium build with conflicting release_extra_cflags setting

R=noelallen@chromium.org

Committed: http://src.chromium.org/viewvc/native_client?view=rev&revision=7417

[Roland McGrath, 2011-12-13 00:07:54]

PTAL

[bradn, 2011-12-13 00:11:41]

lgtm