add short option "-G" for --cmake-generator
add short option "-G" for --cmake-generator

Change-Id: I502bbc77b8f3d9681fafb43e1aa26599d5abf45c

aldebaran/qibuild,dmerejkowsky/qibuild,aldebaran/qibuild,aldebaran/qibuild,dmerejkowsky/qibuild,aldebaran/qibuild,dmerejkowsky/qibuild,dmerejkowsky/qibuild,dmerejkowsky/qibuild