libvpx: add patches for CVE-2019-9232, CVE-2019-9325, CVE-2019-9371, CVE-2019-9433

backports sourced from debian package 1.7.0-3+deb10u1, included in-repo
as file is not available on sources.debian.org or salsa.debian.org

(cherry picked from commit 9bcc7608f26afaf5505146ae5a3be6907f7e3db1)

pkgs/development/libraries/libvpx/default.nix

@@ -65,7 +65,11 @@ stdenv.mkDerivation rec {
     sha256 = "0vvh89hvp8qg9an9vcmwb7d9k3nixhxaz6zi65qdjnd0i56kkcz6";
   };
 
-  patchPhase = ''patchShebangs .'';
+  patches = [
+    ./CVE-2019-9232.CVE-2019-9325.CVE-2019-9371.CVE-2019-9433.patch
+  ];
+
+  postPatch = ''patchShebangs .'';
 
   outputs = [ "bin" "dev" "out" ];
   setOutputFlags = false;