tools lib lk: Fix _FORTIFY_SOURCE builds

Jiri Olsa triggers the following build error:

    SUBDIR ../lib/lk/
    CC debugfs.o
In file included from /usr/include/errno.h:29:0,
                 from debugfs.c:1:
/usr/include/features.h:314:4: error: #warning _FORTIFY_SOURCE requires compiling with optimization (-O) [-Werror=cpp]

This is because enabling buffer overflow checks through _FORTIFY_SOURCE
require compiler optimizations to be enabled too. However, those are
not. Enable them by simply copying the perf optimization level. It can
be expanded later if we want to support debug builds, etc.

Signed-off-by: Borislav Petkov <bp@suse.de>
Reported-by: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/1362338733-8718-1-git-send-email-bp@alien8.de


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>