x11-misc/compose-tables is part of libX11 and checks for x11-base/xorg-proto, x11-libs/libxcb-1.11.1, x11-libs/xtrans during configuration. However, the compilation process seems only involve invocations of C preprocesser. Is it possible to remove dependencies on those X11 libraries?
Trying to rip out X11 from configure.ac seems rather convoluted from a quick look, and running commands from the Makefile.am without running configure seems not much better. Not familiar with these files but looks like static text files, wonder if a pre-generated tarball would be simpler? Think at most may need to sed some paths with ${EPREFIX} in Compose files on install (or maybe they can take relative paths).
Patches welcome—preferably upstream.