Introduce fallback for general cross compilation
The current approach of forcing people to pass the fully qualified prefix
of their toolchain to the configure script is verbose and something of a
chore for people who use the same toolchain to target several devices.
This allows you to set a single toolchain for use with all Qt targets via:
qmake -set CROSS_COMPILE foo
You can still explicitly override this toolchain, as originally mandated,
with the configure time device-option arguments.
Change-Id: Ibd3d940bb08fa09499533f9c661557e337a8421a
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@nokia.com>