Clear temporary directory #163

Job	Run time
ruby-versions / Generate Ruby versions	3s
build (2.5 / ubuntu-latest)	21s
build (2.5 / macos-latest)	3m 20s
build (2.5 / windows-latest)	2m 21s
build (2.6 / ubuntu-latest)	22s
build (2.6 / macos-latest)	1m 3s
build (2.6 / windows-latest)	2m 21s
build (2.7 / ubuntu-latest)	26s
build (2.7 / macos-latest)	54s
build (2.7 / windows-latest)	2m 9s
build (3.0 / ubuntu-latest)	14s
build (3.0 / macos-latest)	18s
build (3.0 / windows-latest)	1m 22s
build (3.1 / ubuntu-latest)	13s
build (3.1 / macos-latest)	33s
build (3.1 / windows-latest)	1m 35s
build (3.2 / ubuntu-latest)	11s
build (3.2 / macos-latest)	19s
build (3.2 / windows-latest)	1m 47s
build (3.3 / ubuntu-latest)	16s
build (3.3 / macos-latest)	19s
build (3.3 / windows-latest)	2m 0s
build (head / ubuntu-latest)	11s
build (head / macos-latest)	32s
build (truffleruby-head / ubuntu-latest)	34s
build (truffleruby-head / macos-latest)	1m 1s
build (mswin / windows-latest)	1m 9s
build (mingw / windows-latest)	1m 36s
	27m 30s

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