unhack Xcode shadow building

explicitly use the correct directories instead of temporarily changing
into the output dir. this makes the code less obfuscated.

Change-Id: Ia935987f486151ae556910703cc20945c7610ffc
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@theqtcompany.com>
Reviewed-by: Joerg Bornemann <joerg.bornemann@theqtcompany.com>