test

Only release the GVL where necessary. #228

Job	Run time
ruby-versions / Generate Ruby versions	3s
build (2.5 / ubuntu-latest)	31s
build (2.5 / windows-latest)	2m 59s
build (2.6 / ubuntu-latest)	29s
build (2.6 / macos-latest)	33s
build (2.6 / windows-latest)	3m 7s
build (2.7 / ubuntu-latest)	26s
build (2.7 / macos-latest)	30s
build (2.7 / windows-latest)	3m 6s
build (3.0 / ubuntu-latest)	14s
build (3.0 / macos-latest)	15s
build (3.0 / windows-latest)	1m 15s
build (3.1 / ubuntu-latest)	16s
build (3.1 / macos-latest)	15s
build (3.1 / windows-latest)	1m 23s
build (3.2 / ubuntu-latest)	13s
build (3.2 / macos-latest)	15s
build (3.2 / windows-latest)	2m 23s
build (3.3 / ubuntu-latest)	15s
build (3.3 / macos-latest)	18s
build (3.3 / windows-latest)	1m 39s
build (head / ubuntu-latest)	12s
build (head / macos-latest)	20s
build (truffleruby-head / ubuntu-latest)	32s
build (truffleruby-head / macos-latest)	22s
build (mswin / windows-latest)	1m 39s
build (mingw / windows-latest)	1m 54s
	25m 24s

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