checking if this helps docker build

CMakeLists.txt

@@ -193,6 +193,9 @@ if(FSFW_BUILD_TESTS)
 
     set(LIB_OS_NAME FreeRTOS)
     target_include_directories(FreeRTOS PUBLIC unittests/testcfg/freertos)
+    set(THREADS_PREFER_PTHREAD_FLAG ON)
+    find_package(Threads REQUIRED)
+    target_link_libraries(FreeRTOS PRIVATE ${CMAKE_THREAD_LIBS_INIT})
   endif()
 
   project(${FSFW_TEST_TGT} CXX C)