don't fail if /etc/issue is not present
don't fail if /etc/issue is not present

Summary:
When running on macOS there is no /etc/issue.  When running
with `set -e` enabled, we don't want this to break the build.

Neither of these is possible today, but will be later in this diff stack.

While I'm in here, also print out the cmake version.

Refs: https://github.com/facebook/watchman/pull/639

Reviewed By: snarkmaster

Differential Revision: D9552416

fbshipit-source-id: 432b5b70678908de9f79787d37c3615a7f8649d3

facebook/wangle,facebook/wangle,facebook/wangle