Auto merge of #178 - rkarp:gnu-win-linking, r=japaric
Auto merge of #178 - rkarp:gnu-win-linking, r=japaric

Fix linking for pc-windows-gnu targets

When linking `std.dll` and the other output executables for `windows-gnu` targets, the linker will complain that various object files are missing. They seem to be necessary only for `windows-gnu`, see also [this function](https://github.com/rust-lang/rust/blob/19e63bd50eb756e35416d7a8f01e2d63f419b373/src/bootstrap/compile.rs#L272).

Tested on Windows 7 64 bit.

japaric/xargo