Add all missing deps for building flatpak

With this flatpak is now possible to build and working

pkgs/flatpak/lib/liba52-prefer-pic.patch

@@ -0,0 +1,39 @@
+From 4c18c43b4d4ccb1d05ae73b813f26ba193fbeee3 Mon Sep 17 00:00:00 2001
+From: Bastien Nocera <hadess@hadess.net>
+Date: Fri, 18 Jan 2019 17:37:13 +0100
+Subject: [PATCH] Prefer PIC
+
+---
+ configure             | 2 +-
+ liba52/configure.incl | 2 +-
+ 2 files changed, 2 insertions(+), 2 deletions(-)
+
+diff --git a/configure b/configure
+index b81fdff..bc0267c 100755
+--- a/configure
++++ b/configure
+@@ -9640,7 +9640,7 @@ _ACEOF
+ 
+ 
+ 
+-LIBA52_CFLAGS="$LIBA52_CFLAGS -prefer-non-pic"
++LIBA52_CFLAGS="$LIBA52_CFLAGS -prefer-pic"
+ 
+ # Check whether --enable-double or --disable-double was given.
+ if test "${enable_double+set}" = set; then
+diff --git a/liba52/configure.incl b/liba52/configure.incl
+index 4dbbcea..5eb69ee 100644
+--- a/liba52/configure.incl
++++ b/liba52/configure.incl
+@@ -2,7 +2,7 @@ AC_SUBST([LIBA52_CFLAGS])
+ AC_SUBST([LIBA52_LIBS])
+ 
+ dnl avoid -fPIC when possible
+-LIBA52_CFLAGS="$LIBA52_CFLAGS -prefer-non-pic"
++LIBA52_CFLAGS="$LIBA52_CFLAGS -prefer-pic"
+ 
+ AC_ARG_ENABLE([double],
+     [  --enable-double         use double-precision samples])
+-- 
+2.20.1
+