Write deterministic local.conf and bblayers.conf

Sort the header sections by their keys and the layers by their names.
This will re-enable writing deterministic config files, and bitbake can
use its cache again, accelerating rebuild startup times a lot.

While at it, indent the layers in bblayers.conf nicely.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>

kas/config.py

@@ -154,7 +154,7 @@ class Config:
             Returns the local.conf header
         """
         header = ''
-        for key, value in self._config.get(header_name, {}).items():
+        for key, value in sorted(self._config.get(header_name, {}).items()):
             header += '# {}\n{}\n'.format(key, value)
         return header