Testing workflow fails due to CMake Error

[jmazanec15]

Failure: https://github.com/opendistro-for-elasticsearch/k-NN/pull/278/checks?check_run_id=1526708387

Error:

 CMake Error at CMakeLists.txt:34 (find_path):
  Could not find NMS_REPO_DIR using the following files: similarity_search

For this action, we use ubuntu-latest, which corresponds to ubuntu 18. Looks like default CMake version changes from 3.17 to 3.19 in this commit: actions/runner-images@5987ab0

Will need to update this line in CMakeLists.txt: https://github.com/opendistro-for-elasticsearch/k-NN/blob/master/jni/CMakeLists.txt#L34