Handle cases where there isn't a BUILDKITE_REPO_SSH_HOST defined.

templates/bootstrap.sh

@@ -144,7 +144,9 @@ else
   # If enabled, automatically run an ssh-keyscan on the git ssh host, to prevent
   # a yes/no promp from appearing when cloning/fetching
   if [[ ! -z "${BUILDKITE_AUTO_SSH_FINGERPRINT_VERIFICATION:-}" ]] && [[ "$BUILDKITE_AUTO_SSH_FINGERPRINT_VERIFICATION" == "true" ]]; then
-    if [[ ! -z "${BUILDKITE_AUTO_SSH_FINGERPRINT_VERIFICATION:-}" ]]; then
+    # Only bother running the keyscan if the SSH host has been provided by
+    # Buildkite. It won't be present if the host isn't using the SSH protocol
+    if [[ ! -z "${BUILDKITE_REPO_SSH_HOST:-}" ]]; then
       : ${BUILDKITE_SSH_DIRECTORY:="$HOME/.ssh"}
       : ${BUILDKITE_SSH_KNOWN_HOST_PATH:="$BUILDKITE_SSH_DIRECTORY/known_hosts"}