I run a very slow computer and compiling using your build.xml but slightly modified for my needs took around 5-10 mins roughly. But then by changing the replace tokens function so only search and replace my sources and not the entire Minecraft sources like it is right now, i have now an average build time of 3 mins. I can make the changes myself and do a merge request if you would like?

Should be a bit faster now - narrowed the scoop of replace tokens to only com.pahimar