Switch to toybox sleep.

Change-Id: I1477527b1b8e09d9955e266a8194da790a9952b3
diff --git a/Android.mk b/Android.mk
index 45992aa..2d22f5c 100644
--- a/Android.mk
+++ b/Android.mk
@@ -184,7 +184,7 @@
 
 # dupes: cat chmod chown cmp cp date df dmesg du grep id ifconfig kill ls mkdir
 #        mknod mkswap mount mv nc netcat nohup notify(inotifyd) printenv readlink renice rm rmdir
-#        sleep swapoff swapon touch umount vmstat
+#        swapoff swapon touch umount vmstat
 # obsolete?: cpio killall5 link unlink
 # non-Linux: count freeramdisk fstype nbd-client oneit vconfig
 # useless?: chvt fsfreeze install makedevs mkfifo mktemp partprobe pivot_root pwdx rev
@@ -244,6 +244,7 @@
     seq \
     setsid \
     sha1sum \
+    sleep \
     sort \
     split \
     stat \