Fix mrpropewr make target to clean debug and release projects

stm-firmware/Makefile

@@ -149,8 +149,16 @@ disassemble: $(target).elf
 objcopy: $(target).bin $(target).hex
 
 mrproper: clean
-	@echo "Purging project files..."
+ifneq ($(DEBUGBUILD),true)
+	@echo "Purging RELEASE project files"
+else
+	@echo "Purging DEBUG project files"
+endif
 	$(QUIET)rm -f $(target).pro $(target).creator $(target).files $(target).cflags $(target).cxxflags $(target).includes $(target).config
+ifneq ($(DEBUGBUILD),true)
+	$(QUIET)$(MAKE) DEBUGBUILD=true mrproper
+endif
+
 
 clean:
 	@echo -n "Cleaning up derived files for "