When trying to build OpenStreetMapView from git://github.com/osmdroid/osmdroid, I get this error:
failed to find target with hash string android-23: D:\\User
The answer to this question.
Gradle gets stupid from time to time and wiping out the cache is the only solution that I've found. You'll find a hidden .gradle folder under your user home folder and another one wherever the checkout location is for osmdroid.