libappindicator won't compile because "g_type_class_add_private" deprecated

[Frank Carlyle McLaughlin]

Attempting to compile libappindicator 12.10.0 from source fails for me on Artix:

app-indicator.c: In function 'app_indicator_init':
app-indicator.c:584:13: error: G_ADD_PRIVATE [-Werror]
  584 | AppIndicatorPrivate * priv = APP_INDICATOR_GET_PRIVATE(self);
      | ^~~~~~~~~~~~~~~
cc1: all warnings being treated as errors

Research suggests that this is may be because "g_type_class_add_private", which is used in app-indicator.c at line 212, is deprecated by glib2, see: https://blog.gtk.org/2018/07/11/news-from-glib-2-58/

Further research suggests that this may be "solvable" by replacing -werror with -wno-error, but that seems like an untidy band-aid at best.

[Sebastien Bacher (seb128)]

Thank you for your bug report, indeed ideally the code would be updated for the new glib but meanwhile not using Werror is an easy workaround