restrict impact of fix for PR 50295 on 'good' VMs to an additional syscall for empty directories rather than an additional call for every directory

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@1036906 13f79535-47bb-0310-9956-ffa450edef68

src/main/org/apache/tools/ant/DirectoryScanner.java

@@ -1248,7 +1248,7 @@ public class DirectoryScanner
             TokenizedPath newPath = new TokenizedPath(path, newfiles[i]);
             File file = new File(dir, newfiles[i]);
             String[] children = file.list();
-            if (children == null || file.isFile()) {
+            if (children == null || (children.length == 0 && file.isFile())) {
                 if (isIncluded(newPath)) {
                     accountForIncludedFile(newPath, file);
                 } else {