fix: do not assume that /usr/bin/env exists on macOS #340

Job	Run time
integration (macos-latest, 3.8)	2m 43s
integration (macos-latest, 3.x)	2m 4s
integration (macos-latest, 3.12)	3m 37s
integration (ubuntu-latest, 3.8)	1m 38s
integration (ubuntu-latest, 3.x)	1m 41s
integration (ubuntu-latest, 3.12)	1m 26s
integration (windows-latest, 3.8)	21m 3s
integration (windows-latest, 3.x)	21m 12s
integration (windows-latest, 3.12)	24m 20s
	1h 19m 44s

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