r211995 - Driver: add a cygwin linker tool

[Rafael Avila de Espindola]

> Driver: add a cygwin linker tool
> 
> This adds a linker tool for the Windows cygwin environment.  This linker
> invocation is significantly different from the generic ld invocation.  It
> requires additional parameters as well as does not accept some normal
> parameters.  This should fix self-hosting on Cygwin.

Nice!

> 
> +  // FIXME: support mudflap: wrap the following:
> +  // -fmudflap || -fmudflapth:
> +  // static const char

Mudflap is dead, no?

https://gcc.gnu.org/gcc-4.9/changes.html

Cheers,
Rafael