So that "make -C tools/perf O=/tmp/some/path" works again.

Problem introduced in:

cd932c59 "perf: Move arch specific code into separate arch director"

Cc: Ian Munsie <imunsie@au.ibm.com>
Cc: Frédéric Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>