Deduplicate qrc files

I'm storing the license texts for our about dialog in a qrc file. So my qrc looks like this:

<RCC>
	<qresource prefix="/licenses">
		<file alias="disclaimer">data/licenses/disclaimer.txt</file>
	</qresource>
	<qresource prefix="/licenses/3rd party">
		<file alias="Qt">data/licenses/qt.txt</file>
		<file alias="OtherLibrary_1">data/licenses/lgpl.txt</file>
		<file alias="OtherLibrary_2">data/licenses/lgpl.txt</file>
	</qresource>
</RCC>

The generated cpp file contains the data/licenses/lgpl.txt within qt_resource_data twice after this, which is a bit unnecessary.

I sadly didn't found a good way to deduplicate this as I iterate over ://licenses/3rd party to check which 3rd party libraries are compiled into our executable (I generate the resource file via CMake).

Therefore, it would be nice if the rcc tool would first collect all file names for the resource file, store the content of the files in `qt_resource_data` and then let the aliases with the same file target point to the same blob view.