libXaw uses ed during configure. checking whether to build shared libraries... yes checking whether to build static libraries... yes checking whether -lc should be explicitly linked in... no creating libtool checking hacks in libtool for libXaw SONAME... ./configure: line 7867: ed: command not found fixed checking for pkg-config... /usr/bin/pkg-config i'm not sure how important this is - it seems to work without it anyways.
You're right, ed is used in configure.ac. I'll fix that.