package/oprofile: fix configure test with gcc 4.9.x

Backport the upstream patch that fix a configure test breaked with gcc 4.9.x.

This patch must be removed with the next version bump.

Fixes:
http://autobuild.buildroot.net/results/f80/f8083f038d0efb7b5becf7810b6fcaf440fb8294/build-end.log



Signed-off-by: Romain Naour <romain.naour@openwide.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>