Merge pull request #3270 from dunhamsteve/impossible-lam #620

Job	Run time
initialise	7s
quick-check	5m 37s
windows-bootstrap-chez	22m 36s
ubuntu-bootstrap-chez	7m 35s
nix-bootstrap-chez	19m 18s
macos-bootstrap-chez	5m 41s
ubuntu-bootstrap-racket	12m 18s
ubuntu-self-host-previous-version	10m 54s
macos-self-host-chez	14m 7s
ubuntu-build-api	4m 1s
ubuntu-self-host-chez	10m 44s
ub-pack-test-pack	11m 46s
ub-test-collie	21s
ub-pack-test-lsp	14m 7s
ub-test-elab-util	40s
ub-test-frex	1m 33s
ub-test-katla-and-html	6m 23s
ubuntu-self-host-racket	0s
windows-self-host-racket	10m 31s
	2h 38m 19s

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