I faced the same issue as jakob with solr-7.6.0, eclipse-2018-12 (4.10.0), Java 1.8.0_191:
*Solution:* In eclipse Run Configuration run-solr remove "file:" from Argument -Dlog4j.configurationFile="file:${workspace_loc:solr-7.6.0}/solr/server/resources/log4j2.xml" -- Sent from: http://lucene.472066.n3.nabble.com/Solr-User-f472068.html