Work around issue with brew and opam #761

Job	Run time
docker-master	1h 32m 0s
publish-standalone-dry-run	14s
test-standalone (master, dev, default)	1m 34s
build-js-of-ocaml (master, 4.11.1)	12m 24s
generated-files (master)	24m 30s
build-wasm-of-ocaml (master, 4.14.1)	16m 43s
standalone-haskell (master)	45m 42s
test-amd64	1h 44m 21s
validate-docker-master	2m 27s
deploy-js-wasm-of-ocaml	31s
docker-check-all	3s
	5h 0m 29s

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