This was a fairly recent update that went unnoticed because it uses a cached variable.
When I previously updated Android cmake I didn't noticed this.
Basically the issue was that Android cmake was no longer setting ${LIBRARY_OUTPUT_PATH_ROOT}
and instead only setting it to ${CMAKE_SOURCE_DIR} if it was passed a variable.
Same PR is open on the android cmake repo here https://github.com/taka-no-me/android-cmake/pull/37
a39eee28e9