libvncserver: add dev output

This will prevent zlib.dev from propagatedBuildInputs from ending in the out closure.

pkgs/development/libraries/libvncserver/default.nix

@@ -16,6 +16,8 @@ stdenv.mkDerivation rec {
   pname = "libvncserver";
   version = "0.9.13";
 
+  outputs = [ "out" "dev" ];
+
   src = fetchFromGitHub {
     owner = "LibVNC";
     repo = "libvncserver";
@@ -23,11 +25,24 @@ stdenv.mkDerivation rec {
     sha256 = "sha256-gQT/M2u4nWQ0MfO2gWAqY0ZJc7V9eGczGzcsxKmG4H8=";
   };
 
-  nativeBuildInputs = [ cmake ];
-  buildInputs = [ libjpeg openssl libgcrypt libpng ]
-    ++ lib.optional stdenv.isLinux systemd
-    ++ lib.optional stdenv.isDarwin Carbon;
-  propagatedBuildInputs = [ zlib ];
+  nativeBuildInputs = [
+    cmake
+  ];
+
+  buildInputs = [
+    libjpeg
+    openssl
+    libgcrypt
+    libpng
+  ] ++ lib.optionals stdenv.isLinux [
+    systemd
+  ] ++ lib.optional stdenv.isDarwin [
+    Carbon
+  ];
+
+  propagatedBuildInputs = [
+    zlib
+  ];
 
   meta = with lib; {
     description = "VNC server library";