Fix broken link in docs.rs (rust-lang#1173)

src/lib.rs

@@ -140,15 +140,14 @@
 //!   set up by running the appropriate developer tools shell.
 //! * Windows platforms targeting MinGW (e.g. your target triple ends in `-gnu`)
 //!   require `cc` to be available in `PATH`. We recommend the
-//!   [MinGW-w64](https://www.mingw-w64.org/) distribution, which is using the
-//!   [Win-builds](http://win-builds.org/) installation system.
+//!   [MinGW-w64](https://www.mingw-w64.org/) distribution.
 //!   You may also acquire it via
 //!   [MSYS2](https://www.msys2.org/), as explained [here][msys2-help].  Make sure
 //!   to install the appropriate architecture corresponding to your installation of
 //!   rustc. GCC from older [MinGW](http://www.mingw.org/) project is compatible
 //!   only with 32-bit rust compiler.
 //!
-//! [msys2-help]: https://github.com/rust-lang/rust#building-on-windows
+//! [msys2-help]: https://github.com/rust-lang/rust/blob/master/INSTALL.md#building-on-windows
 //!
 //! # C++ support
 //!