ABI: Make "linux-generic" ABIs compatible with "linux-*"

This is for the benefit of people using e.g. meego tool chains to
build their own Qt versions and work with them in the desktop
target.

All the specialized targets filter the tool chains again, so
this should be ok to do.

Task-number: QTCREATORBUG-5960
Change-Id: If872d8a6ba75985f23f36646bb89e1651ce82f80
Reviewed-on: http://codereview.qt-project.org/4521


Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Daniel Teske <daniel.teske@nokia.com>