Fix retrieving 'arch' argument in 'osc buildlog'

Author: dmach

osc/commandline.py

@@ -6728,7 +6728,7 @@ def do_buildlog(self, subcmd, opts, *args):
             elif len(args) > 4:
                 raise oscerr.WrongArgs('Too many arguments.')
             else:
-                arch = args[1]
+                arch = args[3]
         else:
             store = osc_store.get_store(Path.cwd())
             store.assert_is_package()