CMake: use Threads::Threads instead of CMAKE_THREAD_LIBS_INIT

Using the more modern imported target does not require a more recent CMake.

Author: Sarcasm

CMakeLists.txt

@@ -41,7 +41,7 @@ add_library(graphqlservice
   Introspection.cpp
   ${CMAKE_BINARY_DIR}/graphqlservice/IntrospectionSchema.cpp)
 target_link_libraries(graphqlservice PRIVATE taocpp::pegtl)
-target_link_libraries(graphqlservice PUBLIC ${CMAKE_THREAD_LIBS_INIT})
+target_link_libraries(graphqlservice PUBLIC Threads::Threads)
 target_include_directories(graphqlservice
   PUBLIC
     $<BUILD_INTERFACE:${CMAKE_SOURCE_DIR}/include>

cmake/cppgraphqlgen-config.cmake

@@ -15,4 +15,5 @@ The following import targets are created
 
 include(CMakeFindDependencyMacro)
 find_package(pegtl REQUIRED)
+find_package(Threads REQUIRED)
 include("${CMAKE_CURRENT_LIST_DIR}/cppgraphqlgen-targets.cmake")