THRIFT-5887: ensure using our CMake modules

Client: cpp

If we append our CMake module path to `CMAKE_MODULE_PATH` and Apache
Thrift is built with FetchContent, our CMake modules in `build/cmake/`
may not be used. Because other paths in `CMAKE_MODULE_PATH` may be
used. For example, both of Apache Arrow and Apache Thrift has
`DefineOptions.cmake`. If Apache Arrow builds Apache Thrift with
FetchContent, Apache Arrow's `DefineOptions.cmake` is used
unexpectedly.
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 50a697b..fc11ec2 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -35,7 +35,7 @@
 message(STATUS "Configuring ${CMAKE_PROJECT_NAME} ${thrift_VERSION}")
 
 
-set(CMAKE_MODULE_PATH "${CMAKE_MODULE_PATH}" "${CMAKE_CURRENT_SOURCE_DIR}/build/cmake")
+list(PREPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/build/cmake")
 
 # Some default settings
 include(DefineCMakeDefaults)