stm: Include libgcc for __aeabi_d2f and __aeabi_f2d functions.

Thanks to Dave Hylands for this.

stm/Makefile

@@ -33,6 +33,7 @@ CFLAGS += -Os -DNDEBUG
 endif
 
 LDFLAGS = --nostdlib -T stm32f405.ld
+LIBS = $(shell $(CC) -print-libgcc-file-name)
 
 SRC_C = \
 	main.c \
@@ -145,7 +146,7 @@ $(BUILD)/flash1.bin: $(BUILD)/flash.elf
 
 $(BUILD)/flash.elf: $(OBJ)
 	$(ECHO) "LINK $@"
-	$(Q)$(LD) $(LDFLAGS) -o $@ $(OBJ)
+	$(Q)$(LD) $(LDFLAGS) -o $@ $(OBJ) $(LIBS)
 	$(Q)$(SIZE) $@
 
 $(BUILD)/%.o: %.s

stm/main.c

@@ -1180,6 +1180,7 @@ soft_reset:
     goto soft_reset;
 }
 
+/* now supplied by libgcc library
 double __aeabi_f2d(float x) {
     // TODO
     return 0.0;
@@ -1189,6 +1190,7 @@ float __aeabi_d2f(double x) {
     // TODO
     return 0.0;
 }
+*/
 
 double sqrt(double x) {
     // TODO