Add Git LFS 2.1.1 to prebuilt x86 image

Git LFS v2.x has a post-checkout hook that verifies support for fetching LFS files. Without the git-lfs binary, fetches in CI builds could fail if the build cache has this hook installed.

There is no official ARM release build at the moment. See https://github.com/git-lfs/git-lfs/issues/623#issuecomment-240554313 for more details.

Closes #2245 (closed)

@stanhu We should run git lfs command to make sure that it is working.

Closing in favor of !588 (merged).

closed