I am going to attach the ebuild.diff. Patches https://overlays.gentoo.org/svn/proj/java/gcj-overlay/dev-java/jdbc-mysql/files/do-not-filter-png.diff https://overlays.gentoo.org/svn/proj/java/gcj-overlay/dev-java/jdbc-mysql/files/no-testsuite.diff
Created attachment 95582 [details, diff] jdbc-mysql.ebuild.diff
Fixed in 3.1.13-r4. Thanks for reporting.