log4j.xml in weld-se-core-1.1.1.Final.jar overrides other (user's) log4j configuration in log4j.properties.
User needs either configure log4j programatically or remove it from the jar manually.

Could it be removed from this jar?

Or if someone really wishes to have some default logging config, there could be an optional dependency on an artifact with this file (+ slf4j-log4j12 and log4j dependencies).