Fail examples target if any example fails

Makefile

@@ -36,7 +36,7 @@ endif
 all: mg_prefix test test++ ex vc98 vc2017 mingw mingw++ linux linux++ infer fuzz
 
 ex:
-	@for X in $(EXAMPLES); do $(MAKE) -C $$X $(EXAMPLE_TARGET); done
+	@for X in $(EXAMPLES); do $(MAKE) -C $$X $(EXAMPLE_TARGET) || break; done
 
 # Check that all external (exported) symbols have "mg_" prefix
 mg_prefix: mongoose.c mongoose.h

examples/stm32-freertos-tcp/Makefile

@@ -52,7 +52,7 @@ SOURCES += $(FREERTOS_PLUS_TCP_PATH)/portable/NetworkInterface/STM32Fxx/stm32fxx
 
 OBJECTS = obj/boot.o $(SOURCES:%.c=obj/%.o)
 
-all: $(PROG).hex
+example: $(PROG).hex
 
 $(PROG).bin: $(PROG).elf
 	$(DOCKER) arm-none-eabi-objcopy -O binary $< $@