Enable warnings in full builds only

Author: tannewt

py/circuitpy_mpconfig.mk

@@ -589,7 +589,7 @@ CIRCUITPY_ULAB_OPTIMIZE_SIZE ?= 0
 CIRCUITPY_VIDEOCORE ?= 0
 CFLAGS += -DCIRCUITPY_VIDEOCORE=$(CIRCUITPY_VIDEOCORE)
 
-CIRCUITPY_WARNINGS ?= 1
+CIRCUITPY_WARNINGS ?= $(CIRCUITPY_FULL_BUILD)
 CFLAGS += -DCIRCUITPY_WARNINGS=$(CIRCUITPY_WARNINGS)
 
 # watchdog hardware support