[Security Solution] Fix a build step when there are no tests to execu…

…te (#165929)

## Summary

Fixes failed build steps when there are no tests to execute and hence no
reports.

## Details

Despite this [PR](#165824) fixes
tests failure when there are no reports but `yarn junit:merge` tries to
convert them to junit format the problem is partially stays as `Failed
Test Reporter` runs for every build step meaning also for successful
build steps. We don't need to handle failed test reports for successful
build steps. There are cases when there are no tests to run so Cypress
doesn't produce reports and nothing is converted to junit format so
`Failed Test Reporter` fails and causes a build step to fails. It could
be solved by defining an environment variable
`DISABLE_MISSING_TEST_REPORT_ERRORS=true` but we need to make sure
reports exist for failed tests. Taking this into account we can rely on
`BUILDKITE_COMMAND_EXIT_STATUS` to avoid running `Failed Test Reporter`
if the build step successed.

One may ask why don't skip `Upload Artifacts` too. We may need some
build artifacts for successful build steps.

---------

Co-authored-by: Tiago Costa <[email protected]>

.buildkite/scripts/lifecycle/post_command.sh

@@ -31,8 +31,10 @@ if [[ "$IS_TEST_EXECUTION_STEP" == "true" ]]; then
   buildkite-agent artifact upload '.es/**/*.hprof'
   buildkite-agent artifact upload 'data/es_debug_*.tar.gz'
 
-  echo "--- Run Failed Test Reporter"
-  node scripts/report_failed_tests --build-url="${BUILDKITE_BUILD_URL}#${BUILDKITE_JOB_ID}" 'target/junit/**/*.xml'
+  if [[ $BUILDKITE_COMMAND_EXIT_STATUS -ne 0 ]]; then
+    echo "--- Run Failed Test Reporter"
+    node scripts/report_failed_tests --build-url="${BUILDKITE_BUILD_URL}#${BUILDKITE_JOB_ID}" 'target/junit/**/*.xml'
+  fi
 
   if [[ -d 'target/test_failures' ]]; then
     buildkite-agent artifact upload 'target/test_failures/**/*'