Fix pre-command to support extended testing (#8418)

(cherry picked from commit 97246c1)

Author: michel-laterman

.buildkite/hooks/pre-command

@@ -73,6 +73,7 @@ if [[ "$BUILDKITE_PIPELINE_SLUG" == "elastic-agent-binary-dra" ]]; then
   fi
 fi
 
-if [[ "$BUILDKITE_PIPELINE_SLUG" == "elastic-agent" && "$BUILDKITE_STEP_KEY" == "integration-fips-cloud-image" ]]; then
+# BUILDKITE_PIPELINE_SLUG should match elastic-agent for PRs, and elastic-agent-extended-tests once it has merged to main
+if [[ "$BUILDKITE_PIPELINE_SLUG" == "elastic-agent"* && "$BUILDKITE_STEP_KEY" == "integration-fips-cloud-image" ]]; then
     docker_login
 fi