message: Add Z_ to VCPKG_CHAINLOAD_TOOLCHAIN_FILE to workaround the regression caused by
diff: @@ -765,7 +765,7 @@ namespace vcpkg::Build
  {"_VCPKG_DOWNLOAD_TOOL", to_string(action.build_options.download_tool)},
  {"_VCPKG_EDITABLE", Util::Enum::to_bool(action.build_options.editable) ? "1" : "0"},
  {"_VCPKG_NO_DOWNLOADS", !Util::Enum::to_bool(action.build_options.allow_downloads) ? "1" : "0"},
  - {"VCPKG_CHAINLOAD_TOOLCHAIN_FILE", action.pre_build_info(VCPKG_LINE_INFO).toolchain_file()},
  + {"Z_VCPKG_CHAINLOAD_TOOLCHAIN_FILE", action.pre_build_info(VCPKG_LINE_INFO).toolchain_file()},
  };
  if (action.build_options.download_tool == DownloadTool::ARIA2)
  