Tweak backtrace.cpp include

Marlin/src/HAL/shared/backtrace/backtrace.cpp

@@ -20,10 +20,9 @@
  *
  */
 
-#include "backtrace.h"
-
 #if defined(__arm__) || defined(__thumb__)
 
+#include "backtrace.h"
 #include "unwinder.h"
 #include "unwmemaccess.h"