Last week Gurjeet Singh asked me about getting the MinGW64 compiler working. When I looked I noticed that they has not made an official build for Mingw hosts (as opposed to linux hosts and darwin hosts) since late 2011. I went on IRC and asked why, and was told that they had switched to GYP to generate builds and it was broken on Mingw. Apparently nobody in the GYP project is interested in fixing it because Mingw isn't one of their supported platforms. Someone gave me this URL that describes the problem: http://code.google.com/p/v8/issues/detail?id=2197#c6
I was, as they say, gobsmacked. Nobody even really seemed to care that much.
If the build tool doesn't support one of your three main target platforms, and moreover it's the only target which isn't cross-compiling, STOP USING IT.