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/fbt/util.py

@@ -2,7 +2,9 @@ import SCons
 from SCons.Subst import quote_spaces
 
 import re
-
+import os
+import random
+import string
 
 WINPATHSEP_RE = re.compile(r"\\([^\"'\\]|$)")
 
@@ -17,3 +19,26 @@ def tempfile_arg_esc_func(arg):
 
 def wrap_tempfile(env, command):
     env[command] = '${TEMPFILE("' + env[command] + '","$' + command + 'STR")}'
+
+
+def link_dir(target_path, source_path, is_windows):
+    # print(f"link_dir: {target_path} -> {source_path}")
+    if os.path.lexists(target_path) or os.path.exists(target_path):
+        os.unlink(target_path)
+    if is_windows:
+        # Crete junction
+        import _winapi
+
+        if not os.path.isdir(source_path):
+            raise Exception(f"Source directory {source_path} is not a directory")
+
+        if not os.path.exists(target_path):
+            _winapi.CreateJunction(source_path, target_path)
+    else:
+        os.symlink(source_path, target_path)
+
+
+def random_alnum(length):
+    return "".join(
+        random.choice(string.ascii_letters + string.digits) for _ in range(length)
+    )