new compile option NANO=YES triggers usage of newlib-nano when linking ARM code.

radio/src/Makefile

@@ -1116,6 +1116,12 @@ MATH_LIB = -lm
 LDFLAGS = -Wl,-Map=$(TARGET).map,--cref
 LDFLAGS += $(MATH_LIB)
 
+
+ifeq ($(NANO), YES)
+#use newlib-nano for linking
+NEWLIB_NANO_FLAGS = --specs=nano.specs -u _printf_float
+endif
+
 # Define Messages
 # English
 MSG_BEGIN = -------- begin --------
@@ -1389,7 +1395,7 @@ OBJS =  $(TMP:.s=.o)
 	@echo
 	@echo $(MSG_COMPILING) $@
 	$(CC) $(ARMCPPFLAGS) $< -o allsrc.o
-	$(CC) $(OBJS) allsrc.o -mcpu=cortex-m3 -mthumb -nostartfiles -lm -T$(LDSCRIPT) -Wl,-Map=$(TARGET).map,--cref,--no-warn-mismatch,--gc-sections -o $@
+	$(CC) $(OBJS) allsrc.o -mcpu=cortex-m3 -mthumb -nostartfiles -lm -T$(LDSCRIPT) -Wl,-Map=$(TARGET).map,--cref,--no-warn-mismatch,--gc-sections $(NEWLIB_NANO_FLAGS) -o $@
 endif
 
 # Target: clean project.