Even on platforms that don't have the new git version, yet.
And using the convoluted way to create an environment variable that should
point to our checked out tree in the GitHub Action. The more obvious ways
have resulted in failed builds for obscure reasons.
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
As some Linux distros start to ship both Qt5 and Qt6, it actually makes more
sense to build only against Qt6 when the user explicitly asks for it. Having it
preferred over Qt5 seems completely wrong in hind sight.
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Hirsute is EOL, so we need to move to Impish.
Adding Fedora 35 allows us to do a simple test against Qt 6.
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
