Previously, we check for RCC support every single time CMake runs.
This is slightly wasteful, and it wasn't being done right anyway.
But it's moot because:
- Calamares supports back to Qt 5.9
- Qt 5.9's version of rcc (at least, 5.9.7) **does** support the
command-line argument `--format-version 1`
- Everything newer does too.
Simplify translations a little, too: just use autorcc rather than
building things by hand.
bfa1f618c7