Don't delete jetty-start when regenerating sha checksums from ant.

lucene/common-build.xml

@@ -2245,6 +2245,12 @@ ${ant.project.name}.test.dependencies=${test.classpath.list}
       <delete>
         <fileset dir="@{dstdir}">
           <include name="**/*.jar.sha1"/>
+
+          <!--
+          Don't delete jetty-start-* because this isn't regerated by ant (but is generated and validated by
+          the gradle build).
+          -->
+          <exclude name="**/jetty-start-*" />
         </fileset>
       </delete>