Add `getOptionalEnvVar` helper #1821

Job	Run time
Upload debug artifacts after failure in analyze (default)	3m 20s
Upload debug artifacts after failure in analyze (stable-v2.20.3)	1m 53s
Upload debug artifacts after failure in analyze (linked)	3m 15s
Upload debug artifacts after failure in analyze (nightly-latest)	3m 21s
Download and check debug artifacts after failure in analyze	11s
	12m 0s

Provide feedback