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/sconsmodular.py

@@ -29,9 +29,20 @@ def BuildModules(env, modules):
     return result
 
 
+def PhonyTarget(env, name, action, source=None, **kw):
+    if not source:
+        source = []
+    phony_name = "phony_" + name
+    env.Pseudo(phony_name)
+    return env.AlwaysBuild(
+        env.Alias(name, env.Command(phony_name, source, action, **kw))
+    )
+
+
 def generate(env):
     env.AddMethod(BuildModule)
     env.AddMethod(BuildModules)
+    env.AddMethod(PhonyTarget)
 
 
 def exists(env):