I am working on a library for processing, using eclipse. And for most part I can manage fine. But...

I am using  commons-lang-2.6 from Apache, which I have put into my sketchfolder/libraries/mylib/library folder for my sketch to run with my own library. But every time I compile my library in eclipse, with new changes, commons-lang-2.6 is deleted from the mylib/library folder. 

Is there some way in eclipse I can add that jar file so that it is included with my library? Or should I put the whole commons-lang-thing somewhere else for it to work with processing?