Qt6 build system should give a list of installed files per Qt module

For Qt6 we want to package binaries per Qt module, not per git module. For this the packaging needs to know which files are part of each Qt module (after make install?).

Proposal:

"make install" would write a file in some format that lists files per Qt module. The file format should also contain the Qt module dependencies.

The dependencies list should also contain the dependencies outside the gitmodule?
Rationale: packaging would need to maintain that list by hand otherwise or parse that information from elsewhere which adds complexity.