Add support of using custom env variables #3035

Job	Run time
check_release	1m 46s
Check Links	4m 36s
build (ubuntu-latest, 3.8)	6m 22s
build (ubuntu-latest, 3.11)	5m 47s
integration_check (ubuntu-latest, 3.8)	2m 26s
integration_check_pypy	2m 50s
build (windows-latest, 3.8)	11m 23s
integration_check (ubuntu-latest, 3.9)	2m 12s
build (windows-latest, 3.11)	10m 31s
integration_check (ubuntu-latest, 3.10)	2m 15s
build (macos-latest, 3.8)	5m 51s
Make SDist	32s
integration_check (ubuntu-latest, 3.11)	2m 20s
build (macos-latest, 3.11)	5m 19s
build (windows-latest, 3.9)	12m 17s
build (ubuntu-latest, pypy-3.8)	12m 48s
Test Docs	1m 7s
Test Examples	52s
build (macos-latest, 3.10)	4m 53s
build (ubuntu-latest, 3.12)	6m 32s
Test Lint	47s
Test Minimum Versions	4m 57s
Test Prereleases	4m 36s
Install from SDist and Test	4m 30s
coverage	8s
tests_check	4s
	1h 57m 41s

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