Add support of using custom env variables #3029

Job	Run time
check_release	19s
integration_check (ubuntu-latest, 3.8)	15s
build (ubuntu-latest, 3.8)	13s
integration_check (ubuntu-latest, 3.9)	20s
Check Links	14s
build (ubuntu-latest, 3.11)	16s
integration_check_pypy	13s
integration_check (ubuntu-latest, 3.10)	11s
build (windows-latest, 3.8)	9s
integration_check (ubuntu-latest, 3.11)	10s
build (windows-latest, 3.11)	11s
Make SDist	17s
Test Docs	18s
build (macos-latest, 3.8)	13s
Test Examples	10s
build (macos-latest, 3.11)	19s
Test Lint	8s
build (windows-latest, 3.9)	9s
build (ubuntu-latest, pypy-3.8)	12s
build (macos-latest, 3.10)	13s
Test Prereleases	15s
Test Minimum Versions	17s
build (ubuntu-latest, 3.12)	19s
Install from SDist and Test	1s
coverage	1s
tests_check	1s
	5m 24s

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