package `qt5quick2-2d-sw-renderer[-GLstubs]`

Both packages share the same source and I'd prefer handling
them in the very same Makefile, but unfortunately that would
create a circular dependency:
`qt5base` depends on `qt5quick2-2d-sw-renderer-GLstubs`, but
`qt5quick2-2d-sw-renderer` depends on `qt5quick2` which
depends on `qt5base`.
`qt5quick2-2d-sw-renderer` and `qt5quick2-2d-sw-renderer-GLstubs`
sharing the same Makefile results in `qt5base` depending on
`qt5quick2` which is meh.