package/x11r7/xlib_libXfont2: work around gcc bug 85180

package/x11r7/xlib_libXfont2: work around gcc bug 85180

On Microblaze, with gcc versions < 8.x the build of xlib_libXfont2
hangs due to gcc bug 85180:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85180.

The bug shows up when building xlib_libXfont2 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/21099d27c03948daaca2d1c149eeba084427e3af/

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