Automatically move programs in sbin to bin

This should fix the OpenJDK build, which was failing because paxctl is
in sbin and therefore not automatically added to $PATH.

http://hydra.nixos.org/build/15658346

pkgs/build-support/setup-hooks/move-sbin.sh

@@ -0,0 +1,19 @@
+# This setup hook, for each output, moves everything in $output/sbin
+# to $output/bin, and replaces $output/sbin with a symlink to
+# $output/bin.
+
+fixupOutputHooks+=(_moveSbin)
+
+_moveSbin() {
+    if [ "$dontMoveSbin" = 1 ]; then return; fi
+    if ! [ -e "$prefix/sbin" ]; then return; fi
+    echo "moving $prefix/sbin/* to $prefix/bin"
+    mkdir -p $prefix/bin
+    shopt -s dotglob
+    for i in $prefix/sbin/*; do
+        mv "$i" $prefix/bin
+    done
+    shopt -u dotglob
+    rmdir $prefix/sbin
+    ln -s bin $prefix/sbin
+}

pkgs/stdenv/generic/default.nix

@@ -44,6 +44,7 @@ let
       ../../build-support/setup-hooks/compress-man-pages.sh
       ../../build-support/setup-hooks/strip.sh
       ../../build-support/setup-hooks/patch-shebangs.sh
+      ../../build-support/setup-hooks/move-sbin.sh
       gcc
     ];