module API: fix out of source builds

test/app/CMakeLists.txt

@@ -2,5 +2,5 @@ add_library(module_api SHARED module_api.c)
 target_link_libraries(module_api -rdynamic)
 set_target_properties(module_api PROPERTIES PREFIX "")
 set_target_properties(module_api PROPERTIES INCLUDE_DIRECTORIES
-    "${CMAKE_SOURCE_DIR}/src/trivia;${CMAKE_SOURCE_DIR}/third_party/luajit/src/")
+    "${CMAKE_BINARY_DIR}/src/trivia;${CMAKE_SOURCE_DIR}/third_party/luajit/src/")
 add_dependencies(module_api generate_module_api)