Add all missing deps for building flatpak

With this flatpak is now possible to build and working

pkgs/flatpak/lib/libdvdcss.json

@@ -0,0 +1,19 @@
+{
+    "name": "libdvdcss",
+    "config-opts": [ "--enable-shared", "--disable-static" ],
+    "sources": [
+        {
+            "type": "git",
+            "url": "https://code.videolan.org/videolan/libdvdcss.git",
+            "tag": "1.4.2",
+            "commit": "7b7c185704567398627ad0f9a0d948a63514394b"
+        },
+        {
+            "type":"script",
+            "commands":[
+                "autoreconf -fiv"
+            ],
+            "dest-filename":"autogen.sh"
+        }
+    ]
+}