.NET "executables" are not executable on Linux

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@275048 13f79535-47bb-0310-9956-ffa450edef68

src/etc/testcases/taskdefs/optional/dotnet.xml

@@ -116,7 +116,9 @@
     </csc>
     <available property="app.created" file="${testCSC.exe}"/>
     <fail unless="app.created">No app ${testCSC.exe} created</fail>
-    <exec executable="${testCSC.exe}" failonerror="true" />
+    <exec executable="mono" failonerror="true">
+      <arg value="${testCSC.exe}"/>
+    </exec> 
     <delete file="${testCSC.exe}"/>
   </target>