libqtav: 1.12.0 -> git-2020-09-10

This un-breaks libqtav by upgrading it to the current upstream HEAD.
Previously, Qtav was broken by the Qt 5.12 -> 5.14 migration (NixOS#84232).
See commit 819bb63

This also un-pins ffmpeg_3; libqtav works fine with current ffmpeg.

Digikam is the only derivation in nixpkgs that has referenced libqtav, thus
upgrading to a pre-release revision poses minimal risk.

pkgs/development/libraries/libqtav/default.nix

@@ -1,27 +1,27 @@
 { mkDerivation, lib, fetchFromGitHub, extra-cmake-modules
 , qtbase, qtmultimedia, qtquick1, qttools
 , libGL, libX11
-, libass, openal, ffmpeg_3, libuchardet
+, libass, openal, ffmpeg, libuchardet
 , alsaLib, libpulseaudio, libva
 }:
 
 with lib;
 
 mkDerivation rec {
   pname = "libqtav";
-  version = "1.12.0";
+  version = "git-2020-09-10";
 
   nativeBuildInputs = [ extra-cmake-modules qttools ];
   buildInputs = [
     qtbase qtmultimedia qtquick1
     libGL libX11
-    libass openal ffmpeg_3 libuchardet
+    libass openal ffmpeg libuchardet
     alsaLib libpulseaudio libva
   ];
 
   src = fetchFromGitHub {
-    sha256 = "03ii9l38l3fsr27g42fx4151ipzkip2kr4akdr8x28sx5r9rr5m2";
-    rev = "v${version}";
+    sha256 = "0qwrk40dihkbwmm7krz6qaqyn9v3qdjnd2k9b4s3a67x4403pib3";
+    rev = "2a470d2a8d2fe22fae969bee5d594909a07b350a";
     repo = "QtAV";
     owner = "wang-bin";
     fetchSubmodules = true;
@@ -46,6 +46,5 @@ mkDerivation rec {
     homepage = "http://www.qtav.org/";
     maintainers = [ maintainers.jraygauthier ];
     platforms = platforms.linux;
-    broken = !(lib.versionOlder qtbase.version "5.13");
   };
 }