package/git: 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 git 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/7ad/7adff001631053ae5a3cb3e176d321f6a2d3cceb/

Signed-off-by: Giulio Benetti <giulio.benetti@micronovasrl.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/git/git.mk

@@ -65,6 +65,14 @@ ifeq ($(BR2_SYSTEM_ENABLE_NLS),)
 GIT_MAKE_OPTS += NO_GETTEXT=1
 endif
 
+GIT_CFLAGS = $(TARGET_CFLAGS)
+
+ifeq ($(BR2_TOOLCHAIN_HAS_GCC_BUG_85180),y)
+GIT_CFLAGS += -O0
+endif
+
+GIT_CONF_OPTS += CFLAGS="$(GIT_CFLAGS)"
+
 GIT_INSTALL_TARGET_OPTS = $(GIT_MAKE_OPTS) DESTDIR=$(TARGET_DIR) install
 
 # assume yes for these tests, configure will bail out otherwise