package/opencv3: fix build due to gcc bug 68485

With Microblaze Gcc version <= 9.x the build fails due to gcc bug 68485:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68485. The bug show up when
building opencv3 with optimization but not when building with -O0. To
work around this, if BR2_TOOLCHAIN_HAS_GCC_BUG_68458=y, we force using
-O0.

Fixes:
 - http://autobuild.buildroot.org/results/c78eac84d1c5a6702e7759cd5364da1c3e399b4b

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Reviewed-by: Giulio Benetti <giulio.benetti@micronovasrl.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/opencv3/opencv3.mk

@@ -23,6 +23,10 @@ ifeq ($(BR2_TOOLCHAIN_HAS_GCC_BUG_64735),y)
 OPENCV3_CXXFLAGS += -DCV__EXCEPTION_PTR=0
 endif
 
+ifeq ($(BR2_TOOLCHAIN_HAS_GCC_BUG_68485),y)
+OPENCV3_CXXFLAGS += -O0
+endif
+
 # OpenCV component options
 OPENCV3_CONF_OPTS += \
 	-DCMAKE_CXX_FLAGS="$(OPENCV3_CXXFLAGS)" \