Tweak CI workflow a bit #24

Job	Run time
FreeBSD-x86_64 with rust stable	1m 7s
Linux-x86_64 with rust stable	1m 3s
Linux-aarch64 with rust stable	1m 23s
Linux-arm with rust stable	1m 17s
Linux-i686 with rust stable	1m 22s
Linux-powerpc64 with rust stable	1m 35s
Linux-powerpc64le with rust stable	1m 31s
Linux-riscv64 with rust stable	1m 8s
Linux-s390x with rust stable	1m 43s
Windows-aarch64 with rust stable	2m 48s
Windows-i686 with rust stable	2m 15s
Windows-x86_64 with rust stable	2m 3s
macOS-x86_64 with rust stable	1m 33s
macOS-aarch64 with rust stable	1m 57s
Linux-x86_64 with rust beta	1m 11s
Linux-x86_64 with rust nightly	1m 7s
	25m 3s

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