add mail plugin dir

Dockerfile

@@ -43,7 +43,7 @@ RUN cd /tmp/dovecot && \
     make install
 
 RUN cd /tmp/pigeonhole && \
-    ./configure \
+    ./configure --prefix '' \
     --with-ldap=yes \
     --with-dovecot=/lib/dovecot \
     --disable-static && \

rootfs/etc/confd/templates/10-mail.conf.tmpl

@@ -6,19 +6,21 @@ namespace inbox {
     auto = subscribe
     special_use = \Junk
   }
- 
+
   mailbox Trash {
     auto = subscribe
     special_use = \Trash
   }
- 
+
   mailbox Sent {
     auto = subscribe
     special_use = \Sent
   }
- 
+
   mailbox Drafts {
     auto = subscribe
     special_use = \Drafts
   }
 }
+
+mail_plugin_dir = /lib/dovecot