Optimize CI a bit #895

Job	Run time
build-jvm-matrix	3s
build (ubuntu-latest, 21)	8m 59s
build (ubuntu-latest, 17)	11m 43s
build (ubuntu-latest, 11)	11m 58s
build (ubuntu-latest, 8)	10m 17s
build (windows-latest, 21)	12m 50s
build (windows-latest, 17)	14m 42s
build (windows-latest, 11)	15m 46s
build (windows-latest, 8)	13m 32s
check_bashisms	4m 1s
check_samples (ubuntu-latest)	3m 55s
check_samples (windows-latest)	5m 34s
	1h 53m 20s

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