FIXUP: Fix top level build again

When we are doing top level build QTWEBENGINE_ROOT/QTWEBENGINE_ROOT_OUT
is not present at configure step, therefore add two ways of calling
checkError, one for configure time and one for make call.

Fix typo in submodule's condition. Add a poor man's workaround
for this test.

Change-Id: Ie95ab9ffe262a45c7e1ea49e4795d142b7df716a
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>