If you are moving towards using agile in developing ant build scripts and need to use Log4j to log build errors(see Log4nt) than you run into the problem of how to enable the eclipse AntClassLoader to pick up the log4j.properties file.  There is a trick to it.

Take and make a global log4j.properties file for all your projects and save it. Now zip that file. Now rename the zipped file to a jar. Now in Eclipse ant preferences run-time add the external jar into the same place as where the ant plugin is showing all the lib entries. Now when you run ant builds that use Log4j.properties and Log4j it will execute correctly and pick up the log4j.properties file to have Eclipse AntClassLoader recognize the log4 appender.