Note that the last upgrade was done by me https://github.com/xwiki/xwiki-platform/commit/8e63ed980a00ac897f2963fdf01bfa77c863dfc1 11 years ago, and unfortunately I don't remember how I created the custom YUICompressor jar... Comparing the standard 2.4.7 version of the YUICompressor jar with the custom 2.4.7-xwiki version shows that we:

• removed the dependency on Rhino (1.6R7)
• excluded the modified Rhino files from the JAR

So we'll have to redo this if it proves that we still need the part of YUICompressor that uses Rhino.