icecat: fix gcc6 build

srcpkgs/icecat/template

@@ -30,6 +30,15 @@ CFLAGS+="\
 	-I${XBPS_CROSS_BASE}/usr/include/nss"
 CXXFLAGS="${CFLAGS}"
 
+_gccver=$(gcc --version | awk '/^gcc \(GCC\)/ { print $3 }')
+if [ "${_gccver%%.*}" -gt 5 ]; then
+	# Append CFLAGS and CXXFLAGS to set work around code which gcc6 would
+	# otherwise regard as out-of-specification and allow it to produce a
+	# working program.
+	CFLAGS+=" -fno-delete-null-pointer-checks -fno-lifetime-dse -fno-schedule-insns2"
+	CXXFLAGS+=" -fno-delete-null-pointer-checks -fno-lifetime-dse -fno-schedule-insns2"
+fi
+
 pre_configure() {
 	case "$XBPS_TARGET_MACHINE" in
 	*-musl)