Add pthread to be linked against

For some reason this was not needed when I built in latest Tumbleweed env.
It seems as if phtread code moved into glibc or something more general,
but this helped to build against Leap 15.4 and Tumbleweed still built
successfully.

Author: watologo1

CMakeLists.txt

@@ -70,6 +70,9 @@ if(OPENSSL_FOUND)
   target_link_libraries(redfish crypto)
 endif()
 
+set(CMAKE_THREAD_PREFER_PTHREAD TRUE)
+set(THREADS_PREFER_PTHREAD_FLAG ON)
+target_link_libraries(redfish Threads::Threads)
 
 add_executable(redfishtest "${CMAKE_CURRENT_SOURCE_DIR}/examples/test.c")
 target_link_libraries(redfishtest redfish)