apr-util: Default database backend appears to be missing

Starting with Alpine 3.13, apr-util switched from Berkeley DB to NDBM as its default database backend due to the deprecation of BDB due to licensing issues (5f13bd26).

However, it appears that while the default --with-dbm= setting as been switched to ndbm, --with-ndbm hasn't been enabled and the headers necessary for compiling in ndbm don't appear to be included in the dependencies either. apr-util seems to silently ignore that fact and just continues to build anyways.

This results in apache2 being unable to do various database-related tasks, such as creating a new lock database for a DAV server:

(20019)DSO load failed: AH00576: The DBM driver could not be loaded
The locks could not be queried for verification against a possible "If:" header.  [500, #0]
Could not open the lock database.  [500, #400]
(20019)DSO load failed: [client 172.21.0.7:37564] Could not open property database.  [500, #1]