Fix overwriting of target via command line with static configs

ConfigStatic does not respect the --target overwrite so far. Fix this
by pulling the default definition into ConfigPython (ConfigStatic
already does that via the Config base class) and set the target provided
via the command line in the static config after parsing all files.

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

kas/build.py

@@ -55,8 +55,7 @@ class Build:
         bld_psr.add_argument('config',
                              help='Config file')
         bld_psr.add_argument('--target',
-                             help='Select target to build',
-                             default='core-image-minimal')
+                             help='Select target to build')
         bld_psr.add_argument('--task',
                              help='Select which task should be executed',
                              default='build')