busybox: Allow running from within the Nix store

This enables running the busybox program directly from the Nix store
(i.e. as /nix/store/<hash>-busybox). We need this for the stdenv
bootstrap.

pkgs/os-specific/linux/busybox/default.nix

@@ -28,6 +28,8 @@ stdenv.mkDerivation rec {
     sha256 = "12v7nri79v8gns3inmz4k24q7pcnwi00hybs0wddfkcy1afh42xf";
   };
 
+  patches = [ ./busybox-in-store.patch ];
+
   configurePhase = ''
     export KCONFIG_NOTIMESTAMP=1
     make ${if enableMinimal then "allnoconfig" else "defconfig"}