Android: Don't bail out if qmlimportscanner is missing.

If the qmlimportscanner is missing, just print the warning and continue,
as it's most likely that the application is a non-qml application.

Change-Id: Ice8b4f11df3df558555fbd3ac373561ce6fb4896
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@theqtcompany.com>