Yesterday luajit-git saw an update that won't install on aarch64, pretty much screwing you over if you wanted to install GIMP. Luckily, I previously installed GIMP just to see if I could and still have the right pkg. If you're facing this issue, I've uploaded a copy of the pkg for you d/l here: [link removed] this link is no longer needed. luajit-git will install from community now.
Install it before installing GIMP, and you should be good to go.
It looks like this has gained attention in some of the right places, so hopefully this post will be moot soon.