media-libs/libexif and media-gfx/exif ARE THE SAME PACKAGE! They have the same versions, they install the same libraries, the same headers, the same pkgconfig files, etc. The only difference between them is that media-gfx/exif additionally installs a perl module and /usr/bin/exif. Since media-libs/exif installs a strict subset of the files installed by media-gfx/exif, my suggestion is to 1. s/libexif/exif/ in ebuilds 2. nuke libexif.
I apologize, brain error.