Fix QEMU compilation with security flags

Fix QEMU compilation with security flags

Since we added compilation security flags (https://gerrit.
automotivelinux.org/gerrit/#/c/5631/), QEMU builds break
when compiling llvm3.3, which is a Mesa dependency.
(most hardware boards do not complain because they do not
rely on Mesa, but on specific graphics drivers instead)

Problem was reported on the mailing list :
https://lists.linuxfoundation.org/pipermail/
automotive-discussions/2016-June/002091.html

This a local backport of the following upstream patch :
http://lists.openembedded.org/pipermail/openembedded-devel/
2016-June/107727.html

Change-Id: Idd378802b303c16de5c0410d533d1680fcef4bb7
Signed-off-by: Manuel Bachmann <mbc@iot.bzh>