cmake: bump Avendish to master

Pick up the addon packaging functions (avnd_addon_package +
avnd_create_{max_addon,touchdesigner,godot}_package with SUPPORT bundling) plus
the accumulated avendish changes.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QYPRqP7mhC5GKDJV4WksZ5

Author: jcelerier

CMakeLists.txt

@@ -18,7 +18,7 @@ if(NOT Avendish_FOUND)
   FetchContent_Declare(
     Avendish
     GIT_REPOSITORY "https://github.com/celtera/avendish"
-    GIT_TAG 9b726a20292c87ea1327e0765e7d2ee8301ec7de)
+    GIT_TAG 6660f3d25924c304e8bf42cae76ab766d23f7dda)
   FetchContent_Populate(Avendish)
   list(APPEND CMAKE_PREFIX_PATH "${avendish_SOURCE_DIR}")
   find_package(Avendish REQUIRED)