-rts_C_SRCS = $(filter-out $(EXCLUDED_SRCS),$(wildcard rts/*.c $(foreach dir,$(ALL_DIRS),rts/$(dir)/*.c)))
-rts_CMM_SRCS = $(wildcard rts/*.cmm)
+rts_C_SRCS := $(filter-out $(EXCLUDED_SRCS),$(wildcard rts/*.c $(foreach dir,$(ALL_DIRS),rts/$(dir)/*.c)))
+rts_CMM_SRCS := $(wildcard rts/*.cmm)