package/asterisk: fix build failure due to gcc bug 93847

The asterisk package exhibits gcc bug 93847 when built for the Nios2
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_93847=y.

Fixes:
http://autobuild.buildroot.net/results/24c0a6ca3b272711a1e6ceaa033925182d0d49c4

Signed-off-by: Giulio Benetti <giulio.benetti@benettiengineering.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
(cherry picked from commit 830fb82822c4a0948fd2dc45ec7851908220e801)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/asterisk/asterisk.mk

@@ -280,6 +280,14 @@ endif
 # Remove default -O3 optimization flag
 ASTERISK_MAKE_OPTS += OPTIMIZE=""
 
+ASTERISK_CFLAGS = $(TARGET_CFLAGS)
+
+ifeq ($(BR2_TOOLCHAIN_HAS_GCC_BUG_93847),y)
+ASTERISK_CFLAGS += -O0
+endif
+
+ASTERISK_CONF_OPTS += CFLAGS="$(ASTERISK_CFLAGS)"
+
 # We want to install sample configuration files, too.
 ASTERISK_INSTALL_TARGET_OPTS = \
 	$(ASTERISK_DIRS) \