mumble_overlay: move from mumble and more fixes

pkgs/applications/networking/mumble/overlay.nix

@@ -0,0 +1,24 @@
+{ stdenv, lib, which, file, mumble, mumble_i686
+}:
+
+let
+  binPath = lib.makeBinPath [ which file ];
+in stdenv.mkDerivation {
+  name = "mumble-overlay-${mumble.version}";
+
+  inherit (mumble) src;
+
+  phases = [ "unpackPhase" "installPhase" "fixupPhase" ];
+
+  installPhase = ''
+    mkdir -p $out/lib
+    ln -s ${mumble}/lib/libmumble.so.1.* $out/lib/libmumble.so.1
+    ${lib.optionalString (mumble_i686 != null) ''
+      mkdir -p $out/lib32
+      ln -s ${mumble_i686}/lib/libmumble.so.1.* $out/lib32/libmumble.so.1
+    ''}
+    install -Dm755 scripts/mumble-overlay $out/bin/mumble-overlay
+    sed -i "s,/usr/lib,$out/lib,g" $out/bin/mumble-overlay
+    sed -i '2iPATH="${binPath}:$PATH"' $out/bin/mumble-overlay
+  '';
+}