Support building JDK for Windows

[Marcono1234]

As pointed out in #3 it might be useful to allow building the JDK for Windows as well.
Some JDK Java source files are OS specific; the current Linux build only seems to compile Linux and Unix (and for JDK 8 Solaris?) Java source files, but no Windows specific Java source code.

The JDK building guide indicates that this is possible using WSL (though most likely only for newer JDK versions).
This might require a separate Dockerfile.

Edit: Building using WSL is most likely not desirable because the build would then depend on the host environment and would require modifying it (e.g. installing Visual Studio).
It might be possible to use Docker Windows Containers instead (see Docker documentation), but that requires Windows 10 Professional or Enterprise (see documentation). The build could be based on the configuration the OpenJDK is using for their GitHub workflow.

[Dark403969]

#3