Summary:
This PR paves the way for nightly builds.
+ Get rid of cmake 3.17 manual install as cmake 3.18 is now available
in conda.
+ Update docker files for conda packages.
+ Specify CUDA architectures via CMake's `CMAKE_CUDA_ARCHITECTURES`.
Pull Request resolved: https://github.com/facebookresearch/faiss/pull/1422
Reviewed By: mdouze
Differential Revision: D23870447
Pulled By: beauby
fbshipit-source-id: 40ae7517e83356443a007a43261713e7e3a140d4