It turns out it was a stupid build problem on my machine: I didn't have libexif-dev installed on either of my Ubuntu systems, and GIMP's configure script wasn't warning me about it in any obvious way. (Of course, had I taken the time to read through the 3679 lines of config.log, the information was buried in there around line 2199.)
So now I have EXIF again, at least on the laptop (hooray!) but I also learned something more important: after running configure for the first time on any new system, before running make, do this:
grep -i "will not" config.log
That may not flag everything, but at least it's a start at getting a list of features that have been disabled because of dependencies you forgot to install (anything which configure is smart enough to tell you "will not be built").
Schumaml had the great idea of putting a list of enabled features in the About box. Maybe I'll look into doing that in a week or two (when the current crunch is over and I have more time to upgrade my development machine so that it can use gtk 2.8 and I can actually build GIMP again).
Update: I added a printout similar to the one I thought I remembered, so there should be no further need to grep for "will not".
[ 15:11 Jan 24, 2006 More gimp | permalink to this entry | comments ]