$NetBSD$

Do not build included libwebp, use system one.

--- third_party/CMakeLists.txt.orig	2019-10-23 23:54:06.000000000 +0000
+++ third_party/CMakeLists.txt
@@ -34,8 +34,8 @@ endif()
 
 if(WITH_WEBP_SUPPORT)
   # Enable img2webp so "webpmux" library is built
-  set(WEBP_BUILD_IMG2WEBP ON CACHE BOOL "Build the img2webp animation tool.")
-  add_subdirectory(libwebp)
+  #set(WEBP_BUILD_IMG2WEBP ON CACHE BOOL "Build the img2webp animation tool.")
+  #add_subdirectory(libwebp)
 endif()
 
 if(NOT USE_SHARED_TINYXML)
