Added support for windows platforms using mingw.

[jarredholman]

Adds windows support using mingw compiler that comes with rubyinstaller's devkit.

Also requires Python27 (official windows build) and msysgit.

To build, open cmd.exe shell

set PATH=%PATH%;C:\Python27;C:\Program Files (x86)\Git\bin
c:\ruby-devkit-mingw64\devkitvars.bat
bundle install
bundle exec rake compile

mingw-generate-makefiles.sh script is a modified version from v8 source (modification just adds x64 target).

[cowboyd]

Are there any hosted CI solutions that support windows builds?

[ignisf]

I don't believe I've heard of any

[jarredholman]

Could try http://www.appveyor.com/ ?

[cowboyd]

Looks promising. I've set up a project there to build libv8 https://ci.appveyor.com/project/cowboyd/libv8

but it looks like it needs an appveyor.yml to get working. It should build pull requests, if you have any experience with appveyor, it would be awesome if you could submit one to get it working :)

[jarredholman]

I haven't used it before but it doesn't look too hard so I'll have a go at it.

[jarredholman]

Added a first attempt. I only really tested that it worked for ruby21-x64 but I've enabled all the ruby versions to see what happens.

There is one slight problem. It rebuilds v8_base again for the "host" after doing it for the "target" so that it can run "tools_gyp_v8_gyp_js2c_host_js2c".
This is making the build get dangerously close to the 30 minute time limit.

I looked at the Travis CI log and it seems like the linux build doesn't do that so I'm not sure why this would be different.

[jarredholman]

Seems like the time was not as bad as I thought...

[cowboyd]

Whoa, that was easy. If you're ok with this @ignisf, let's merge it.