qtmod_test.pl: support shadow build/install for modules outside of qt5
qtmod_test.pl: support shadow build/install for modules outside of qt5

The initial implementation of building with installation (both shadow
build and non-shadow build) didn't attempt to handle Qt modules
hosted outside of qt5.git; update it to work for this case.

Change-Id: If18cff49c35bc7a6116907902f3c0424c263ea3a
Sanity-Review: Qt Sanity Bot <5581206bb7e0307f0d99eb71898ae6b694149ca5@ovi.com>
Reviewed-by: Toby Tomkins <23ead35e36f9890dd80f47acf9947179b1bd7fe7@nokia.com>

tsarajar/qtqa,tsarajar/qtqa,tsarajar/qtqa,tsarajar/qtqa