--- cmake/xxhash.cmake	2026-07-08 17:07:40.000000000 +0800
+++ cmake/xxhash.cmake	2026-07-12 00:26:27.000000000 +0800
@@ -12,4 +12,8 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-set(_gRPC_XXHASH_INCLUDE_DIR "${CMAKE_CURRENT_SOURCE_DIR}/third_party/xxhash")
+if(NOT gRPC_XXHASH_INCLUDE_DIR)
+  set(_gRPC_XXHASH_INCLUDE_DIR "${CMAKE_CURRENT_SOURCE_DIR}/third_party/xxhash")
+else()
+  set(_gRPC_XXHASH_INCLUDE_DIR "${gRPC_XXHASH_INCLUDE_DIR}")
+endif()