X libraries not found?

The position of X libraries is stored, for instance for pre-compiled PM3 LINUXELF binaries, in the template file m3config/src/LINUXELF as well as in X11/LINUXELF/.M3EXPORTS (m3build/templates/LINUXELF, and X11R4/LINUXELF/.M3EXPORTS for SRC-M3). Thus you may want to edit these files if your X libraries are located in an uncommon place.