Build: Make Zstandard use our zstd library

This makes it so that we can update to newer Zstandard versions without having to worry about zstd library version mismatches (Zstandard bundled their own zstd version)

Pull Request: https://projects.blender.org/blender/blender/pulls/138777

build_files/build_environment/cmake/zstandard.cmake

@@ -28,7 +28,10 @@ ExternalProject_Add(external_zstandard
 
   BUILD_COMMAND
     ${PYTHON_BINARY} setup.py
-      build ${ZSTANDARD_BUILD_OPTION} -j${PYTHON_MAKE_THREADS}
+      --system-zstd
+      build_ext ${ZSTANDARD_BUILD_OPTION} -j${PYTHON_MAKE_THREADS}
+      --include-dirs=${LIBDIR}/zstd/include
+      --library-dirs=${LIBDIR}/zstd/lib
       install
       --old-and-unmanageable