busybox add initramfs hook

sys/base/busybox/files/busybox.initramfs

@@ -0,0 +1,39 @@
+#!/bin/sh
+
+# This hook copies busybox binary into the initramfs directory
+# and creates all necessary links to it.
+# It should be placed last into the hooks directory, in order to
+# not overwrite commands which are provided by other means.
+
+set -e
+
+case "${1:-}" in
+  prereqs)  echo ""; exit 0;;
+esac
+
+BB_BIN=/bin/busybox
+
+[ n = "$BUSYBOX" ] && exit 0
+
+[ -r /usr/share/initramfs-tools/hook-functions ] || exit 0
+. /usr/share/initramfs-tools/hook-functions
+
+if [ -f $DESTDIR/bin/sh ] && cmp -s $DESTDIR/bin/sh $BB_BIN ; then
+  # initramfs copies busybox into /bin/sh, undo this
+  rm -f $DESTDIR/bin/sh
+fi
+rm -f $DESTDIR/bin/busybox	# for compatibility with old initramfs
+copy_exec $BB_BIN /bin/busybox
+
+for alias in $($BB_BIN --list-long); do
+  alias="${alias#/}"
+  case "$alias" in
+    # strip leading /usr, we don't use it
+    usr/*) alias="${alias#usr/}" ;;
+    */*) ;;
+    *) alias="bin/$alias" ;;  # make it into /bin
+  esac
+
+  [ -e "$DESTDIR/$alias" ] || \
+    ln "$DESTDIR/bin/busybox" "$DESTDIR/$alias"
+done