The configure script blocks java 11 because it only recognizes up to java 9. The build also uses an old version of asm, which fails to run on Java 9+. (see this: https://issues.apache.org/jira/browse/WW-4866) With the current ebuilds of sys-libs/db, users may not use java 11 (even after unmasking the virtual), however imo it is still important to report the problem.
*** This bug has been marked as a duplicate of bug 713866 ***