docs: update installation instructions for Linux #86

Job	Run time
install-cross (linux-musl)	4s
macos (stable, aarch64-apple-darwin)	40s
windows (stable, i686-pc-windows-msvc)	3m 10s
windows (stable, x86_64-pc-windows-msvc)	3m 10s
linux (stable, aarch64-unknown-linux-musl)	1m 10s
linux (stable, arm-unknown-linux-musleabi)	1m 26s
linux (stable, arm-unknown-linux-gnueabi)	1m 7s
linux (stable, armv7-unknown-linux-gnueabihf)	1m 17s
linux (stable, armv7-unknown-linux-musleabihf)	1m 10s
linux (stable, i686-unknown-linux-musl)	1m 15s
linux (stable, x86_64-unknown-linux-musl)	1m 5s
	15m 34s

Provide feedback