CI: Build on Ubuntu 20.04 for arm64 linux release #2001

Job	Run time
build-spidermonkey-win	14s
build-spidermonkey-unix (ubuntu-22.04, 3.10)	15s
sdist	34s
build-spidermonkey-unix (macos-13, 3.10)	20s
build-spidermonkey-unix (ubuntu-22.04-arm, 3.10)	1m 21s
build-spidermonkey-unix (macos-14, 3.10)	15s
build-and-test	0s
publish-nightly	0s
publish	0s
publish-archive	0s
	2m 59s

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