Fix DLL build on Windows

Author: wravery

src/CMakeLists.txt

@@ -356,6 +356,14 @@ if(GRAPHQL_UPDATE_VERSION)
   update_version_rc(graphqlclient)
 endif()
 
+if(WIN32 AND BUILD_SHARED_LIBS)
+  target_compile_definitions(graphqlclient
+    PUBLIC GRAPHQL_DLLEXPORTS
+    PRIVATE IMPL_GRAPHQLCLIENT_DLL)
+
+  add_version_rc(graphqlclient)
+endif()
+
 # RapidJSON is the only option for JSON serialization used in this project, but if you want
 # to use another JSON library you can implement an alternate version of the functions in
 # JSONResponse.cpp to serialize to and from GraphQLResponse and build graphqljson from that.