Just so you don't think I stopped, I thought I'd give you a bit of an update. I finally found out how to make the cross-compile work in Linux, now I just need to (really) understand how compiler and linker directives and flags work. There's still a bit of a disconnect in my mind that I'm working on. The fallout of this is that I broke my Linux Gimp installation and had to fix it.
Don't know if you noticed, but there are new development versions (0.1.3) of BABL and GEGL in the git repository; they haven't been made available as tarballs yet. On a related note, I wondered if you went through the compilegimp.sh script and updated all of the various source package versions. Nearly all of them have new releases since the script was last updated. Be aware when/if you do this to note that some of the dependencies names have subtle changes - most have hyphens replaced by underscores, and I think all now have the "_win32" after the version numbers. It took me an hour or so to track down all the changes.
I also found out that the script doesn't work in the Linux terminal if you type sh compile-gimp.sh. Doing it in this fashion invokes the wrong shell, and some of the commands inside the script fail.
This probably won't affect the compiling on a Windows host through MinGW/MSYS as I think they use a bash shell already, which looks to be the type of shell the script was written for. Also (in my opinion), the script is way too complicated. I think 60% of the script is variables for parts of package names!