need to add a path separator after the first path element, not before it

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@735676 13f79535-47bb-0310-9956-ffa450edef68

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

@@ -373,10 +373,11 @@ public class PathConvert extends Task {
                 // Now convert the path and file separator characters from the
                 // current os to the target os.
 
-                if (first) {
+                if (!first) {
                     rslt.append(pathSep);
-                    first = false;
                 }
+                first = false;
+
                 StringTokenizer stDirectory = new StringTokenizer(elem, fromDirSep, true);
 
                 while (stDirectory.hasMoreTokens()) {