package/asterisk: remove default -O3 optimization flag

Actually asterisk package gets built with -O3 cflag since it's defaulted
into its sources, but it's not what we want, so let's empty its OPTIMIZE
Makefile variable letting Buildroot CFLAGS to take place instead.

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

package/asterisk/asterisk.mk

@@ -280,6 +280,9 @@ ifeq ($(BR2_TOOLCHAIN_HAS_LIBATOMIC),y)
 ASTERISK_MAKE_OPTS += ASTLDFLAGS="-latomic"
 endif
 
+# Remove default -O3 optimization flag
+ASTERISK_MAKE_OPTS += OPTIMIZE=""
+
 # We want to install sample configuration files, too.
 ASTERISK_INSTALL_TARGET_OPTS = \
 	$(ASTERISK_DIRS) \