Android: Fix Windows build with recent SDK

Since the dx tool has moved in the SDK, we need to update our copy
of it to also search in the new location for dx.jar.

Task-number: QTBUG-31405
Change-Id: If093a9f51f33c5d8666919f516a3b336322a7169
Reviewed-by: Ray Donnelly <mingw.android@gmail.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Reviewed-by: Paul Olav Tvete <paul.tvete@digia.com>