Add all missing deps for building flatpak

With this flatpak is now possible to build and working

pkgs/flatpak/gstreamer-1.0/gstreamer-vaapi.json

@@ -0,0 +1,17 @@
+{
+    "name": "gstreamer-vaapi",
+    "buildsystem": "meson",
+    "config-opts": [
+        "-Ddoc=disabled",
+        "-Dexamples=disabled",
+        "-Dtests=disabled"
+    ],
+    "sources": [
+        {
+            "type": "git",
+            "url": "https://gitlab.freedesktop.org/gstreamer/gstreamer-vaapi.git",
+            "tag": "1.18.1",
+            "commit": "f9e925af3645439f7b7a4580700fcd6ce17fc1c9"
+        }
+    ]
+}