Resolve build hysteresis with system-test

Per AI summary:
  > On a clean build, the "System tests" module (packages/system-test) could fail because it depends on an un-attached ZIP artifact (org.dcache:dcache-plugin-hsqldb:zip). The HSQLDB plugin produced its ZIP via the assembly plugin but didn’t attach it, so a first-run reactor build couldn’t resolve the ZIP until a prior install populated the local repository (commonly by running with -DskipTests). Attaching the ZIP fixes first-run builds.

Author: greenc-FNAL

plugins/hsqldb/pom.xml

@@ -31,6 +31,7 @@
                       <format>zip</format>
                   </formats>
                   <appendAssemblyId>false</appendAssemblyId>
+                  <attach>true</attach>
               </configuration>
               <executions>
                   <execution>