The ebuild for dev-java/jflex-1.4.1 needs the patch jflex-1.4.1-build.xml.patch which is not on portage. Reproducible: Always Steps to Reproduce:
Created attachment 124436 [details] This is the patch. The patch was present in java-exp overlay, but the developer that added jflex to the main portage tree apparently forgot it (I think it's ali_bush).
Added the patch to portage. My apologies for missing it and thank you for the bug report.