Switch to sha256

git-svn-id: https://svn.apache.org/repos/asf/xmlgraphics/fop-pdf-images/trunk@1825964 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/build.xml b/build.xml
index 970b75c..4f63273 100644
--- a/build.xml
+++ b/build.xml
@@ -484,7 +484,7 @@
       <include name="maven/pom.xml"/>
       </patternset>
     </fileset>
-    <checksum algorithm="sha256">
+    <checksum algorithm="sha-256" fileext=".sha256">
       <fileset refid="bundle-files"/>
     </checksum>
     <input message="Passphrase for your default private key (attention: passphrase will be echoed in clear text on the display!)" addproperty="pwd"/>