[Development] Modify QLibraryInfo to support any default location of qt.conf

[Oswald Buddenhagen]

On Thu, Jan 28, 2016 at 10:47:21AM +0100, Maximilian Hrabowski wrote:
> 1. Add a new public API: static void QLibraryInfo::setQtConfFilePath( const QString& filePath) which defaults to ":/qt/etc/qt.conf“ and is used in QSettings *QLibraryInfoPrivate::findConfiguration() instead of the hard-coded path.
> 2. Also lookup qt.conf in all of QLibraryInfo::libraryPaths() (this is how we got the plugins found)
> 3. introduce an environment variable that points to the qt.conf similar to the one of QWebEngineProcess.exe
> 
> Please comment.
> 
you should contribute to
https://bugreports.qt.io/browse/QTBUG-14150 getting fixed.
that (specifically, subtask https://bugreports.qt.io/browse/QTBUG-15234)
will make everything relative to the location of qtcore (or ideally,
relative to the particular library which is doing the resource lookup).
this will ultimately cause the disappearance of qt.conf, which sounds a
lot better to me than either of your options.