ci: fix Arduino + Pico SDK jobs #46

Job	Run time
Host tests (ubuntu-latest)	15s
Strict warnings (gcc + clang) (gcc, g++)	11s
Strict warnings (gcc + clang) (clang, clang++)	19s
Host tests (macos-latest)	18s
Arduino compile (rp2040:rp2040:rpipico)	45s
Pico SDK build (examples/rp2040-midi2)	6h 0m 14s
	6h 2m 2s

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