configure: fix bogus message about not needing to install qt

when building additional modules against an already installed qtbase,
$$[QT_INSTALL_PREFIX/get] is obviously the same as
$$[QT_INSTALL_PREFIX], so we would misdiagnose a non-prefix build.

instead, use the same condition as qt_build_config.prf (we cannot just
rely on what it sets, because in qtbase configure context it's evaluated
before we set up the paths).

Fixes: QTBUG-60541
Change-Id: I37be30e0e682ece76ed460a66f1984ee0fe2ed71
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@qt.io>

0 files changed, 0 insertions, 0 deletions