Return back LINKFLAGS for debug mode

platformio/builder/tools/piomisc.py

@@ -322,7 +322,7 @@ def ConfigureDebugFlags(env):
     env.Append(CPPDEFINES=["__PLATFORMIO_BUILD_DEBUG__"])
 
     debug_flags = ["-Og", "-g3", "-ggdb3"]
-    for scope in ("ASFLAGS", "CCFLAGS"):
+    for scope in ("ASFLAGS", "CCFLAGS", "LINKFLAGS"):
         _cleanup_debug_flags(scope)
         env.Append(**{scope: debug_flags})