rcc: Remove directory restriction between location of qrc file and it's files

It would be very nice to be able to compile qrc files with content that's not in a subdir of the .qrc file itself.

We have quite a lot of data (20-600 Mb / app) that we can't check into our DVCS (obviously). So, we keep it on network share and use an rsync-like tool) but it would be nice to be able to embed those into a single binary file, and Qt's resource system seems excellent for that.

But as the qrc files are in VCS, it's cumbersome. For now, the workaround, which I haven't implemented, seems to be to copy the qrc files to the appropriate local content dir, invoke rcc there, then remove the qrc file.

A single option in rcc that specifies the directory where content is would solve this nicely.