package/lua-cqueues: fix build failure due to gcc bug 68485

package/lua-cqueues: fix build failure due to gcc bug 68485

The lua-cqueues 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/c35964dda4e2328c2c1f3b2388677b68c5ed461e/

Signed-off-by: Giulio Benetti <giulio.benetti@micronovasrl.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>