fix gpio->app_hal dependencies

app/Arduino.h

@@ -1,7 +1,7 @@
 extern "C" {
     #include "main.h"
     #include "cmsis_os.h"
-    #include "gpio.h"
+    #include "app_hal.h"
     #include <stdio.h>
 }
 

target_prod/Makefile

@@ -96,7 +96,7 @@ startup_stm32l476xx.s
 CPP_SOURCES = ../app/app.cpp
 
 C_SOURCES += ../app/write.c
-C_SOURCES += ../app/gpio.c
+C_SOURCES += ../app/app_hal.c
 
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 # binaries