Add Windows and Powershell support #353

Job	Run time
install-cross (linux-musl)	6s
macos (stable, x86_64-apple-darwin)	1m 5s
macos (beta, x86_64-apple-darwin)	1m 37s
macos (nightly, x86_64-apple-darwin)	1m 21s
linux (stable, arm-unknown-linux-gnueabi)	1m 22s
linux (stable, armv7-unknown-linux-gnueabihf)	1m 36s
linux (stable, i686-unknown-linux-musl)	1m 39s
linux (stable, x86_64-unknown-linux-musl)	1m 36s
linux (stable, aarch64-unknown-linux-gnu)	1m 20s
linux (stable, aarch64-unknown-linux-musl)	1m 32s
linux (stable, arm-unknown-linux-gnueabihf)	1m 31s
linux (beta, arm-unknown-linux-gnueabi)	1m 28s
linux (beta, armv7-unknown-linux-gnueabihf)	1m 32s
linux (beta, i686-unknown-linux-musl)	1m 32s
linux (beta, x86_64-unknown-linux-musl)	1m 32s
linux (beta, aarch64-unknown-linux-gnu)	1m 25s
linux (beta, aarch64-unknown-linux-musl)	1m 49s
linux (beta, arm-unknown-linux-gnueabihf)	1m 31s
linux (nightly, arm-unknown-linux-gnueabi)	1m 28s
linux (nightly, armv7-unknown-linux-gnueabihf)	1m 32s
linux (nightly, i686-unknown-linux-musl)	1m 43s
linux (nightly, x86_64-unknown-linux-musl)	2m 1s
linux (nightly, aarch64-unknown-linux-gnu)	1m 39s
linux (nightly, aarch64-unknown-linux-musl)	1m 49s
linux (nightly, arm-unknown-linux-gnueabihf)	1m 44s
	37m 30s

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