[Development] configure qtbase on mac os

[Chris Meyer]

I'm configuring qtbase (Mac OS 10.6.8, Xcode 4.2, and qtbase/master)
using the following command:

export QTDIR=/some/path/for/installation
./configure -prefix $QTDIR -opensource -no-sql-mysql -qt-libpng
-qt-libjpeg -no-dbus -nomake examples -nomake demos

After a while, I get an error that configure cannot determine
big-endian or little-endian. However, these options seem to be
required only if I'm building with the -qpa option, which should
default to off.

It looks like the variable $PLATFORM_MAC is not being set properly. Is
this something that needs to be specified on the command line or is
the machinery for automatically setting $PLATFORM_MAC broken?