Regression: Qt doesn't use libc method to get locale for libxkbcommon

The offending commit is: https://github.com/qt/qtbase/commit/73ea9f032864566cc019d286b2f210b78cd70a3d

It falsely thinks that applications have to call setlocale for this to work, but they don't need in fact as Qt does that for them, here: https://github.com/qt/qtbase/blob/365904085e27b49d402e389d5c454781eca4f3f5/src/corelib/kernel/qcoreapplication.cpp#L563

Looking at the issue it was intended to fix (QTBUG-85529) the cause is most likely user misconfiguration; the user likely forgot to generate the locale, that could be discovered with:

locale -a

Now, given that Qt doesn't use libc's method, it also doesn't convert the aliases and entering accents fails as soon as the user has set

LANG=en_US.UTF8

rather than

LANG=en_US.UTF-8

(setlocale would return normalized en_US.UTF-8 that works with xkbcommon).