Remove sysroot detection

Remove sysroot detection

configure parses the compiler from the mkspecs using an awk script.
The detected compiler is then used to determine sysroot support.
The awk script is currently unable to handle loading of qmake
features and thus configure will not detect the compiler correctly.

This is the case when using device profiles. The qdevice.pri is loaded
through the qmake feature file device_config.prf.

One possible way to fix this is to move this detection after qmake is
built and make this a .pro based config.test. However, this cannot be done
because the sysroot is actually baked into the qmake binary as the
QT_SYSROOT variable.

The solution is to remove this check completely and let the build fail
when Qt starts compiling with --sysroot.

Change-Id: I6c3b7ec2c8e5e390d6f5b1e602d656682d610b98
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@nokia.com>