And no stack trace for classic compiler either.

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@268103 13f79535-47bb-0310-9956-ffa450edef68

src/main/org/apache/tools/ant/taskdefs/Javac.java

@@ -484,7 +484,11 @@ public class Javac extends MatchingTask {
             throw new BuildException("Cannot use classic compiler, as it is not available", location);
         }
         catch (Exception ex) {
-            throw new BuildException("Error starting classic compiler: ", ex, location);
+            if (ex instanceof BuildException) {
+                throw (BuildException) ex;
+            } else {
+                throw new BuildException("Error starting classic compiler: ", ex, location);
+            }
         }
     }