Allow HOMEBREW_PREFIX replacement in external patches #30875

Job	Run time
syntax	53s
cask audit	2m 26s
tap syntax	6m 4s
vendored gems	43s
formula audit	4m 29s
test default formula (Ubuntu 22.04)	1m 25s
tests (online)	5m 16s
test default formula (Ubuntu 20.04)	3m 33s
update-test (Ubuntu 22.04)	30s
tests (generic OS)	3m 13s
test default formula (macOS 13 x86_64)	3m 44s
update-test (macOS)	26s
tests (Ubuntu 22.04)	3m 18s
test default formula (macOS 15 arm64)	1m 22s
tests (Ubuntu 20.04)	3m 54s
tests (macOS 13 x86_64)	7m 7s
tests (macOS 15 arm64)	5m 19s
	53m 42s

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