qitoolchain create: bug fixes
qitoolchain create: bug fixes

* Fix crash when using --cmake-generator
* --cmake-generator no longer requires a worktree

Change-Id: Idf2576687854b8dc5a47d0b64ba6eca15840d281

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