Add `getOptionalEnvVar` helper #10705

Job	Run time
check-codeql-versions	35s
analyze-other (python)	58s
analyze-other (actions)	51s
analyze-javascript (ubuntu-22.04, linked)	4m 8s
analyze-javascript (ubuntu-22.04)	4m 6s
analyze-javascript (windows-2022)	6m 2s
analyze-javascript (windows-2025, linked)	5m 58s
analyze-javascript (ubuntu-24.04)	4m 9s
analyze-javascript (macos-14, linked)	5m 33s
analyze-javascript (windows-2022, linked)	5m 44s
analyze-javascript (ubuntu-24.04, linked)	4m 9s
analyze-javascript (macos-13)	8m 35s
analyze-javascript (windows-2025)	7m 16s
analyze-javascript (macos-13, linked)	11m 57s
analyze-javascript (macos-14)	9m 32s
analyze-javascript (macos-15)	5m 42s
analyze-javascript (macos-15, linked)	6m 56s
	1h 32m 11s

Provide feedback