Add sel4-deps for macOS, style the build_sdk now #1515

Job	Run time
clippy_check	36s
Freeze Code	13s
rustfmt_check	16s
Checks / Trailing Whitespace	4s
Checks / Portable Shell	21s
Checks / Style	38s
Checks / Gitlint	37s
Build SDK / Build SDK (Linux x86_64)	31m 30s
Build SDK / Build SDK (macOS, all targets)	26m 10s
	1h 0m 25s

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