anchor.diff:  , sshSupport ? true, libssh2
   , mysqlSupport ? false, libmysqlclient
   , postgresqlSupport ? false, postgresql
  +, ipmiSupport ? false, openipmi
   }:
   
   # ensure exactly one primary database type is selected
  
positive.code:       ++ optional snmpSupport "--with-net-snmp"
        ++ optional sshSupport "--with-ssh2=${libssh2.dev}"
        ++ optional mysqlSupport "--with-mysql"
        ++ optional postgresqlSupport "--with-postgresql";
  
        prePatch = ''
          find database -name data.sql -exec sed -i 's|/usr/bin/||g' {} +
  
negative.code:       ++ optional snmpSupport net-snmp
        ++ optional sshSupport libssh2
        ++ optional mysqlSupport libmysqlclient
        ++ optional postgresqlSupport postgresql
        ++ optional ipmiSupport openipmi;
  
        configureFlags = [
          "--enable-server"
  