Add musl build action #9

Job	Run time
Build x86_64-unknown-linux-musl	2m 20s
Build x86_64-pc-windows-msvc	3m 3s
Build macOS universal binary	1m 46s
Build i686-unknown-linux-gnu	2m 45s
Build x86_64-unknown-linux-gnu	2m 33s
Build armv7-unknown-linux-gnueabihf	2m 37s
Build i686-pc-windows-msvc	3m 3s
Build aarch64-unknown-linux-musl	2m 23s
Build aarch64-unknown-linux-gnu	2m 45s
	23m 15s

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