Windows nightlies have statically linked rustc/rustdoc binaries

[alexcrichton]

They're around 40MB in size, which would be ridiculously large for a dynamically linked binary.

I've confirmed that the OSX/linux nightlies are indeed dynamically linked.

[alexcrichton]

This appears to be because we install from stage3 on windows, which is hard-wired to produce statically linked binaries because I thought stage3 was only used for snapshots.

[alexcrichton]

Closed by efec34a