Add musl build action #23

Job	Run time
Build aarch64-unknown-linux-musl	2m 54s
Build i686-unknown-linux-gnu	2m 51s
Build x86_64-pc-windows-msvc	2m 49s
Build x86_64-unknown-linux-gnu	2m 33s
Build aarch64-unknown-linux-gnu	2m 46s
Build armv7-unknown-linux-gnueabihf	2m 48s
Build x86_64-unknown-linux-musl	2m 52s
Build macOS universal binary	2m 18s
Build i686-pc-windows-msvc	2m 57s
	24m 48s

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