fbt: support for LOADER_AUTOSTART; post-build size stats (#1594)

* fbt: restored LOADER_AUTOSTART support
* scripts: added fwsize.py wrapper for size command; fbt: changed size post-build stats to fwsize.py call
* fbt: removed size wrapper
* fbt: added stats for binary flash size in pages
* fbt: hint on build options details
* scripts: fixed fwsize.py for *nix

site_scons/site_tools/fbt_apps.py

@@ -51,7 +51,7 @@ def DumpApplicationConfig(target, source, env):
 def build_apps_c(target, source, env):
     target_file_name = target[0].path
 
-    gen = ApplicationsCGenerator(env["APPBUILD"])
+    gen = ApplicationsCGenerator(env["APPBUILD"], env.subst("$LOADER_AUTOSTART"))
     with open(target_file_name, "w") as file:
         file.write(gen.generate())