fix fixup_directory managment

- box depenedent fixups have the form to_system_<box.typ>
- name of fixup directories have to determined after reading config

install.py

@@ -321,7 +321,6 @@ installs = set()
 box = BoxInfo()
 box.fixup_dirs = [  # (src, dst, as_root)
     (TOOLS / 'to_system', Path('/'), True),
-    (TOOLS / f'to_system_{box.typ}', Path('/'), True),
     (TOOLS / 'to_home', Path.home(), False),
 ]
 box.hostname_changed = False
@@ -592,7 +591,8 @@ def walk_dir(action, srcpath, dstroot, files):
                             print('ERROR: %s in %s, but also in repo -> ignored' % (fname, DEL))
                         else:
                             to_delete.append(fname)
-                action.delete(to_delete)
+                if to_delete:
+                    action.delete(to_delete)
         if missing:
             action.missing(missing)
 
@@ -862,6 +862,10 @@ def handle_config():
                            ' net.ifnames=0'):
             do_cmd('update-grub')
 
+    boxsys = TOOLS / f'to_system_{box.typ}', Path('/'), True
+    if boxsys not in box.fixup_dirs:
+        box.fixup_dirs.append(boxsys)
+
     result = [f'config file:\n  {cfgfile}']
     for section, section_dict in config.items():
         result.append(section)