This reverts commit c686e885c0
and commit d64abf8166.
We don't feature .qmake.cache/.qmake.super files anymore in the
source directory, so there's no problem anymore.
Change-Id: Ib820a109fbfbad70d85b0f14ef72915882217ca3
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>