If the local version of Qt is older than the minimum version required by
yuzu, download a pre-built binary package from yuzu-emu/ext-linux-bin
and build yuzu with it, instead.
This also requires linking yuzu to the correct libraries after building
it, and copying over the required binaries when building yuzu.
This sets the Qt requirement to 5.12, which is intentionally behind the
versions used by our toolchains since they are not all updated yet to
5.15.
With shader caches on the horizon, one requirement is to provide visible
feedback for the progress. The shader cache reportedly takes several
minutes to load for large caches that were invalidated, and as such we
should provide a loading screen with progress.
Adds a loading screen widget that will be shown until the first frame of
the game is swapped. This was chosen in case shader caches are not being
used, several games still take more than a few seconds to launch and
could benefit from a loading screen.
