Improve how mac packaging scripts divide Qt into sub-packages

The binary packages for Mac each contain a number of sub-packages, currently debuglibraries, docs, examples, headers, imports, libraries, plugins, tools, and translations.

The packaging script (mkdist/installers/mac-binary/package/mkpackage) extracts a Qt source package, configures it, builds it, then calls a set of small scripts to create each sub-package (mkdist/installers/mac-binary/install/<package>/create-package.sh).

The knowledge of which files from the compiled Qt directory tree belong to which sub-package is hard-coded into the individual create-package.sh scripts. This is a significant maintenance problem as new build products (e.g. new libraries, new file types, qmlimports) in the directory tree are often omitted from the sub-packages and we (release managers) often only find out about the omissions after packages have been released.

To fix, it would be preferable for the build system to correctly partition these files. Then the packaging scripts can pickup all libraries in a directory, or similarly all the examples in a directory. The set of sub-packages is fairly orthogonal to the Qt modules being discussed in the modularization project, so we cannot rely on a solution falling out of the modularization activity.