Subzero: Correct the cross test's diagnostic message for a test failure.

BUG= none
R=jvoung@chromium.org

Review URL: https://codereview.chromium.org/1195553002
diff --git a/pydir/crosstest_generator.py b/pydir/crosstest_generator.py
index e79657f..b5d64ab 100755
--- a/pydir/crosstest_generator.py
+++ b/pydir/crosstest_generator.py
@@ -176,6 +176,7 @@
                   f.write(' '.join(cmp_cmd) + ' && \\\n')
                   f.write(run_cmd + '\n')
                   f.write('echo Recreate a failure using ' + __file__ +
+                          ' --toolchain-root=' + args.toolchain_root +
                           ' --include=' + ','.join(desc) + '\n')
                   f.write('# CHECK: Failures=0\n')
               else: