QtIFW

Fix installer executable creation in Linux

If Linux has several partitions and tmp is pointing to a different
partition than where we are trying to create installer executable with
binarycreator, binarycreator fails with 'Invalid cross-device link'.
Fixed so that tmp is not used when creating an installer executable.

Change-Id: Ieee52ee1929f980345a7940dd381cc94dbf3d40e
Reviewed-by: Iikka Eklund <iikka.eklund@qt.io>
Reviewed-by: Katja Marttila <katja.marttila@qt.io>