dell-command-configure: fix missing include in wrapper (NixOS#368471)

Author: wegank

pkgs/by-name/de/dell-command-configure/package.nix

@@ -70,7 +70,7 @@ let
   };
 
 in
-stdenv.mkDerivation rec {
+stdenv.mkDerivation {
   inherit version;
   pname = "dell-command-configure";
 

pkgs/by-name/de/dell-command-configure/wrapper-lib.c

@@ -1,5 +1,6 @@
 #include <stdio.h>
 #include <string.h>
+#include <unistd.h>
 
 static const char from[] =  "/usr/lib/ext/dell/omreg.cfg";
 static const char to[] = "@to@";