package/fwts: fix build with BR2_OPTIMIZE_0

Fixes:
http://autobuild.buildroot.net/results/fab/fabd031d38cb618cdb11b4a86cd853b0da61695b/

Signed-off-by: Bernd Kuhls <bernd@kuhls.net>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/fwts/fwts.mk

@@ -15,6 +15,10 @@ FWTS_DEPENDENCIES = host-bison host-flex host-pkgconf libglib2 libbsd \
 	$(if $(BR2_PACKAGE_BASH_COMPLETION),bash-completion) \
 	$(if $(BR2_PACKAGE_DTC),dtc)
 
+ifeq ($(BR2_OPTIMIZE_0),y)
+FWTS_CONF_ENV = CFLAGS="$(TARGET_CFLAGS) -O1"
+endif
+
 ifeq ($(BR2_PACKAGE_FWTS_EFI_RUNTIME_MODULE),y)
 FWTS_MODULE_SUBDIRS = efi_runtime
 $(eval $(kernel-module))