So presumably after compiling libast you have done a make install?
The question is when you did a make install, into which directories did it install the header and library files?
When you try to compile Eterm, is it complaining about a missing libast header file or the libast library file?
If you have installed either of these in non-standard places, have you specified when you ran the configure script for Eterm, extra directories to check for header (include) files and library files?
Have you checked the configure.log file for Eterm, after you ran configure, as to whether or not it found libast and what was the problem, if any?