tools lib api: Undefine _FORTIFY_SOURCE before setting it
tools lib api: Undefine _FORTIFY_SOURCE before setting it

Some toolchains (like Hardened Gentoo) define _FORTIFY_SOURCE in the
built-in, default args.  This causes perf builds to fail with:

<command-line>:0:0: error: "_FORTIFY_SOURCE" redefined [-Werror]
<built-in>: note: this is the location of the previous definition cc1:
all warnings being treated as errors

To avoid this, undefine _FORTIFY_SOURCE before (possibly re-)defining it
in tools/lib/api.

v2 applies cleanly on top of already pulled kbuild changes for 4.1-rc1.

Signed-off-by: Bobby Powers <ab5c1f9fe62b73e39ab6f9824010ebb63b35f2c7@gmail.com>
Acked-by: Jiri Olsa <2c6594f608aa3d41e98d48846a6328831f7084ad@kernel.org>
Cc: Dirk Gouders <a00b27378a09822d5638cdfb8c2e7ccc36d74c56@gouders.net>
Cc: Michal Marek <0c835876a532a476f30fdb1f6e963bae6c5a1a04@suse.cz>
Cc: Paul Mackerras <19a0ba370c443ba08d20b5061586430ab449ee8c@samba.org>
Cc: Peter Zijlstra <645ca7d3a8d3d4f60557176cd361ea8351edc32b@chello.nl>
Cc: 5594068016b1f67c422b8e8c1fc41f56f0491834@vger.kernel.org
Link: http://lkml.kernel.org/r/1429658381-3039-1-git-send-email-ab5c1f9fe62b73e39ab6f9824010ebb63b35f2c7@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <293abb6b76d7791c0732cc517d38c4b5c734b87f@redhat.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs