i18n() calls gettext, which only after some setlocale(LC_ALL, ""); starts
to look for env variables when deciding on the language catalog to use.
That call is done during QApp instance creation.
See also https://phabricator.kde.org/D5439#102005 and
https://phabricator.kde.org/D5455
Discussion if that is supposed to be like that has to be continued,
but for now this change should keep KDevelop on the safe side.