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 <[email protected]>
Acked-by: Jiri Olsa <[email protected]>
Cc: Dirk Gouders <[email protected]>
Cc: Michal Marek <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: [email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

0 files changed, 0 insertions, 0 deletions