ash,hush: add TODO for rare build failure

*: remove some redundant includes

coreutils/dd.c

@@ -8,7 +8,6 @@
  * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
  */
 
-#include <signal.h>  /* For FEATURE_DD_SIGNAL_HANDLING */
 #include "libbb.h"
 
 /* This is a NOEXEC applet. Be very careful! */

coreutils/tee.c

@@ -11,7 +11,6 @@
 /* http://www.opengroup.org/onlinepubs/007904975/utilities/tee.html */
 
 #include "libbb.h"
-#include <signal.h>
 
 int tee_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int tee_main(int argc, char **argv)