package: fix cmake packages build with ninja

+= is needed for CMAKE_OPTIONS.

mt76 needs Ninja disabled as the kernel stuff uses normal make.

Signed-off-by: Rosen Penev <rosenp@gmail.com>

package/system/ubus/Makefile

@@ -53,7 +53,7 @@ endef
 TARGET_CFLAGS += -I$(STAGING_DIR)/usr/include -flto
 TARGET_LDFLAGS += -flto
 
-CMAKE_OPTIONS = \
+CMAKE_OPTIONS += \
 	-DLUAPATH=/usr/lib/lua \
 	-DABIVERSION="$(PKG_ABI_VERSION)"
 

package/system/uci/Makefile

@@ -55,7 +55,7 @@ endef
 TARGET_CFLAGS += -I$(STAGING_DIR)/usr/include
 TARGET_LDFLAGS += -L$(STAGING_DIR)/usr/lib
 
-CMAKE_OPTIONS = \
+CMAKE_OPTIONS += \
 	-DLUAPATH=/usr/lib/lua \
 	$(if $(DEBUG),-DUCI_DEBUG=ON)