Set flag CMAKE_THREAD_PREFER_PTHREAD

CMakeLists.txt

@@ -71,7 +71,8 @@ set(TESTS_ANSWERER_SOURCES
     ${CMAKE_CURRENT_SOURCE_DIR}/test/p2p/answerer.cpp
 )
 
-set(THREADS_PREFER_PTHREAD_FLAG ON)
+set(CMAKE_THREAD_PREFER_PTHREAD TRUE)
+set(THREADS_PREFER_PTHREAD_FLAG TRUE)
 find_package(Threads REQUIRED)
 
 add_subdirectory(deps/usrsctp EXCLUDE_FROM_ALL)