remove pointless initialization of qmakespec

we have proper fallback paths further down the line.

Change-Id: I3648cc985d21bbec4c2c24e179830db4467af210
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>
(cherry picked from qtbase/0dedf8c3403923b963c51eb65d9cbe838d5ba0d4)
Reviewed-by: Daniel Teske <daniel.teske@digia.com>