package/x11r7/xlib_libXfont: work around gcc bug 85180

package/x11r7/xlib_libXfont: work around gcc bug 85180

With Microblaze Gcc version < 8.x the build hangs due to gcc bug
85180: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85180. The bug
shows up when building xlib_libXfont with optimization but not when
building with -O0. To work around this, if
BR2_TOOLCHAIN_HAS_GCC_BUG_85180=y we force using -O0.

Fixes:
http://autobuild.buildroot.net/results/7c6/7c64becbf06a1e00e41b7ddb95dd0c65bf364eb7/

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