You also have to install the java (and if you want java.ssdebug) Mercury grades with the following prefix /usr/local/mercury-11.07.1 .
Check out this video:
For some kind of inputs (like a file without module previously), the compile might not terminate, making any further editing, building impossible. In this case please report this file to our mailing list, and try to fix it outside of eclipse (you have to restart eclipse, or kill the mercury_compile process).
The generated sources are not deleted, so sometimes a clean build might be necessary, and in case of errors in .m files older -successfully built- java files will be used, so please be careful with this kind of errors.
The Mercury library is not added to the classpath, the source folder is not src/main/mercury, but simply src. It is in Other (or Xtext if installed) category, not Mercury or kai or something similar.
TODO, not tested, the dependencies may be not considered.