Add support of using custom env variables #3063

Job	Run time
integration_check (ubuntu-latest, 3.8)	2m 20s
check_release	1m 57s
integration_check (ubuntu-latest, 3.9)	2m 21s
build (ubuntu-latest, 3.8)	6m 4s
integration_check (ubuntu-latest, 3.10)	2m 21s
Check Links	4m 49s
build (ubuntu-latest, 3.11)	6m 12s
build (windows-latest, 3.8)	11m 17s
integration_check_pypy	2m 42s
integration_check (ubuntu-latest, 3.11)	2m 21s
Make SDist	22s
build (windows-latest, 3.11)	8m 52s
build (macos-latest, 3.8)	5m 49s
Test Docs	1m 4s
build (macos-latest, 3.11)	4m 39s
Test Lint	41s
Test Examples	43s
build (windows-latest, 3.9)	12m 6s
build (ubuntu-latest, pypy-3.8)	12m 22s
Test Minimum Versions	4m 58s
build (macos-latest, 3.10)	5m 53s
Test Prereleases	4m 42s
build (ubuntu-latest, 3.12)	7m 3s
Install from SDist and Test	4m 28s
coverage	11s
tests_check	2s
	1h 56m 19s

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