linphone-desktop: Fix missing ringtones

The Linphone installed from nixpkgs was not able to play the ringtone
for an incoming call.

The reason for this was the ringtone audio files are part of the
`linphonePackages.liblinphone` package itself, but belong to
`linphonePackages.liblinphone`.

However, they were were not linked to where the
`linphonePackages.linphone-desktop` package expected them to be.

This commit fixes that.

pkgs/applications/networking/instant-messengers/linphone/linphone-desktop/default.nix

@@ -139,7 +139,6 @@ stdenv.mkDerivation (finalAttrs: {
 
   preInstall = ''
     mkdir -p $out/share/linphone
-    mkdir -p $out/share/sounds/linphone
     mkdir -p $out/share/belr
   '';
 
@@ -156,6 +155,9 @@ stdenv.mkDerivation (finalAttrs: {
     ln -s ${mediastreamer2}/lib/mediastreamer/plugins/* $out/lib/mediastreamer/plugins/
     ln -s ${grammars} $out/share/belr/grammars
 
+    mkdir -p $out/share/sounds/linphone/
+    ln -s ${liblinphone}/share/sounds/linphone/rings $out/share/sounds/linphone/rings
+
     wrapProgram $out/bin/linphone \
       --unset QML2_IMPORT_PATH \
       --set MEDIASTREAMER_PLUGINS_DIR $out/lib/mediastreamer/plugins