mumble: Fix build with boost version 1.66

This is already tracked in upstream issue mumble-voip/mumble#3281 and a
fix has been merged in mumble-voip/mumble@caa187373ec2f8bcf5b88e6340973.

The patch I'm adding here is using the merged commit
mumble-voip/mumble@ea861fe86743c8402bbad77d8d1dd9de8dce447e and I've
only added it for the stable release because the patch is already
included in the git version.

@pbogdan also had a similar commit to this
(pbogdan/nixpkgs@8029edea298b36df6494885055c8bf123aa4d26b), but the
patch was applied to both stable and git and thus the git version would
have been broken.

Tested by building mumble and mumble_git and running the mumble NixOS VM
test.

Signed-off-by: aszlig <[e-mail]>
Cc: @viric, @jgeerds, @abbradar
Fixes: #33655

pkgs/applications/networking/mumble/default.nix

···
-{ stdenv, fetchurl, fetchgit, pkgconfig
+{ stdenv, fetchurl, fetchgit, fetchpatch, pkgconfig
 , qt4, qmake4Hook, qt5, avahi, boost, libopus, libsndfile, protobuf, speex, libcap
 , alsaLib, python
 , jackSupport ? false, libjack2 ? null
···
   generic = overrides: source: stdenv.mkDerivation (source // overrides // {
     name = "${overrides.type}-${source.version}";
 
-    patches = optional jackSupport ./mumble-jack-support.patch;
+    patches = (source.patches or []) ++ optional jackSupport ./mumble-jack-support.patch;
 
     nativeBuildInputs = [ pkgconfig python ]
       ++ { qt4 = [ qmake4Hook ]; qt5 = [ qt5.qmake ]; }."qt${toString source.qtVersion}"
···
       url = "https://github.com/mumble-voip/mumble/releases/download/${version}/mumble-${version}.tar.gz";
       sha256 = "1s60vaici3v034jzzi20x23hsj6mkjlc0glipjq4hffrg9qgnizh";
     };
+
+    # Fix compile error against boost 1.66 (#33655):
+    patches = singleton (fetchpatch {
+      url = "https://github.com/mumble-voip/mumble/commit/"
+          + "ea861fe86743c8402bbad77d8d1dd9de8dce447e.patch";
+      sha256 = "1r50dc8dcl6jmbj4abhnay9div7y56kpmajzqd7ql0pm853agwbh";
+    });
   };
 
   gitSource = rec {