add support for x86_64-w64-mingw32 and cut the fat from libgcj

[Brian Jones]

I believe the idea of including only code which you specify is required came up before on the list many years ago.  Hopefully a search through archives can be instructive.

Brian 

> On Dec 24, 2017, at 2:44 PM, Yale Zhang <yzhang1985@gmail.com> wrote:
> 
> Greetings. I have a patch that allows GNU java to target MingW64
> (host=GNU/Linux only). Are you guys still taking patches now that Java
> has been removed from GCC 7? Or would it be more appropriate to host
> it on my own website or instructables.com?
> 
> I also have another patch that cuts all the GUI, cryptography, and non
> UTF8/16 charset support from libgcj. This reduces the size of
> statically linked EXEs a lot (~27MiB to 4.5 MiB for a hello world
> program). This is important for a legacy utility that other developers
> use on Windows and who don't want to install a Java runtime.
> 
> Commenting out and deleting code is a crude way to do, I know. Should
> use conditional compilation and even explore what's causing GUI code
> to be dragged into a hello world program. Maybe dead code removal
> isn't working (need to compile with -ffunction-sections and
> --gc-sections?)
> 
> appreciate your feedback,
> -Yale