This fixes a problem when the preprocessing scripts were called from a
path with spaces in it.
Task-number: QTBUG-15317
Change-Id: I92ea85e12e2f9abfc262a8dcaa4f414e471e468c
Reviewed-by: João Abecasis <joao@abecasis.name>
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>