Build NSIS installer for rust toolchain on windows

[graydon]

The NSIS ( http://nsis.sourceforge.net ) installer is probably the best bet for deployment on windows. Make a basic package that installs rustc and the docs and libs to C:\Program Files\Rust or such.

[espindola]

I am not familiar with windows, but since I am doing the driver side I can give this a try.