Add cleanup of /kernel.old and /modules.old, per Leigh's suggestion.

utils/tbbuildkernels

@@ -41,6 +41,12 @@ chdir($SRCDIR) or die "Unable to change to $SRCDIR: $!\n";
 build_kernel($MAINKERNEL,1);
 install_kernel($MAINKERNEL,1,["kernel", @MAINKERNEL_ALIASES]);
 
+#
+# Clean up kernel.old and modules.old
+#
+system "rm -f /kernel.old" and die "Unable to remove /kernel.old\n";
+system "rm -rf /modules.old" and die "Unable to remove /modules.old\n";
+
 #
 # Now, build the rest!
 #