package/proj: fix build failure due to gcc bug 68485

package/proj: fix build failure due to gcc bug 68485

The proj package exhibits gcc bug 68485 when built for the Microblaze
architecture with optimization enabled, which causes a build failure.

As done for other packages in Buildroot work around this gcc bug by
setting optimization to -O0 if BR2_TOOLCHAIN_HAS_GCC_BUG_68485=y.

Fixes:

http://autobuild.buildroot.net/results/e61/e61bd55067071415223e523a81de3c2e9cafea6f/

Signed-off-by: Giulio Benetti <giulio.benetti@micronovasrl.com>
Tested-by: Zoltan Gyarmati <zgyarmati@zgyarmati.de>
Acked-by: Zoltan Gyarmati <zgyarmati@zgyarmati.de>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>