Avoid printing generic and duplicated "checking for QT" during ./configure

Summary:
Print "checking for QT4" and "checking for QT5" instead

This is a backport of Core's PR10549

Test Plan:

../configure
make

Reviewers: #bitcoin_abc, jasonbcox

Reviewed By: #bitcoin_abc, jasonbcox

Subscribers: teamcity

Differential Revision: https://reviews.bitcoinabc.org/D1817