Setup nightly builds for new Android NDK builds in released Qt versions

Since NDK versions can change during the lifetime of a Qt version, we want to have nightly builds for new NDK (compared to the version of initial Qt release) to ensure that the released Qt can still handle the new NDK versions.

This is then meant to setup the nightly build for this where the build can run against a WIP patch that has the update without having to merge the NDK update directly to the branch.