fix the extension for the download

Author: benfry

build/build.xml

@@ -168,7 +168,7 @@
       https://github.com/adoptium/temurin11-binaries/releases/download/jdk-11.0.12%2B7/OpenJDK11U-jdk_x64_mac_hotspot_11.0.12_7.tar.gz
     -->
 
-    <property name="jdk.download.url" value="https://github.com/adoptium/temurin11-binaries/releases/download/jdk-${jdk.train}.${jdk.version}.${jdk.update}%2B${jdk.build}/OpenJDK11U-jdk_x64_${jdk.download.os}_hotspot_${jdk.train}.${jdk.version}.${jdk.update}_${jdk.build}.tar.gz" />
+    <property name="jdk.download.url" value="https://github.com/adoptium/temurin11-binaries/releases/download/jdk-${jdk.train}.${jdk.version}.${jdk.update}%2B${jdk.build}/OpenJDK11U-jdk_x64_${jdk.download.os}_hotspot_${jdk.train}.${jdk.version}.${jdk.update}_${jdk.build}.${jdk.download.ext}" />
 
     <get src="${jdk.download.url}"
          dest="${jdk.tgz.path}"