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.
- The new format was introduced in Qt 5.7, and Qt 5.9 introduced
the --format-version flag to rcc to switch back to the reproducible
format 1. For distro's with Qt 5.7, don't use the new flag.
- Reported from Neptune Linux, #979
The RCC output files in version 2 contain a timestamp of the
source file, which changes per build. Drop down to version 1,
which just removes the timestamp.
See reproducible builds note 'timestamps in source generated by rcc'.
FIXES#917
Since we install the CMake files now, also put license headers in them.
These files are intended to help plugin and branding component authors
write them in a simple Calamares-idiomatic way.
