fbt: fixes (#1352)

* fbt: added --git-tasks; fixed typos
* fbt: fixed --extra-int-apps handling; scripts: moved storage.py & selfupdate.py to App() framework
* fbt: changed pseudo-builders to PhonyTargets with commands; added link to latest build dir as build/latest
* fbt: Restored old ep git handling
* fbt: dropped git tasks & dirlink.py
* fbt: removed extra quoting in fbt.cmd
* docs: added flash_usb to ReadMe.md

Co-authored-by: あく <alleteam@gmail.com>

site_scons/site_tools/gdb.py

@@ -11,22 +11,6 @@ def generate(env):
         GDBCOM="$GDB $GDBOPTS $SOURCES",  # no $TARGET
         GDBPYCOM="$GDBPY $GDBOPTS $GDBPYOPTS $SOURCES",  # no $TARGET
     )
-    env.Append(
-        BUILDERS={
-            "GDB": Builder(
-                action=Action(
-                    "${GDBCOM}",
-                    "${GDBCOMSTR}",
-                ),
-            ),
-            "GDBPy": Builder(
-                action=Action(
-                    "${GDBPYCOM}",
-                    "${GDBPYCOMSTR}",
-                ),
-            ),
-        }
-    )
 
 
 def exists(env):