perf tools: Fix test_on_exit for 32-bit build

perf tools: Fix test_on_exit for 32-bit build

builtin-record.c:42:12: error: static declaration of 'on_exit' follows non-static declaration
In file included from util/util.h:51:0,
                 from builtin.h:4,
                 from builtin-record.c:8:
/usr/include/stdlib.h:536:12: note: previous declaration of 'on_exit' was here

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/r/1382099356-4918-12-git-send-email-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>