os/mac/diagnostic: improve OpenCore check #31225

Job	Run time
syntax	46s
tap syntax	6m 53s
cask audit	2m 21s
formula audit	4m 40s
tests (online)	5m 1s
test default formula (Ubuntu 22.04)	1m 38s
tests (generic OS)	3m 1s
update-test (Ubuntu)	23s
tests (Ubuntu 24.04)	2m 56s
update-test (macOS)	20s
vendored gems	32s
test default formula (Ubuntu 20.04)	2m 48s
tests (Ubuntu 22.04)	3m 7s
test default formula (macOS 13 x86_64)	3m 41s
tests (Ubuntu 20.04)	4m 2s
test default formula (macOS 15 arm64)	1m 24s
tests (macOS 13 x86_64)	12m 12s
tests (macOS 15 arm64)	5m 24s
	1h 1m 9s

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