Don't write temporary files just to satisfy CMake

Instead tell CMake that it's a generated source file so that it accepts
their absence at generation time.

Author: muggenhor

CMakeLists.txt

@@ -193,8 +193,9 @@ else()
         set(CUKE_DYNAMIC_CPP_STEPS "${CUKE_TEST_FEATURES_DIR}/step_definitions/cpp_steps.cpp")
         string(REPLACE "/tmp" "${CMAKE_FILES_DIRECTORY}/e2e-steps.dir/tmp" CUKE_DYNAMIC_CPP_STEPS_OBJ "${CUKE_DYNAMIC_CPP_STEPS}${CMAKE_CXX_OUTPUT_EXTENSION}")
 
-        file(WRITE ${CUKE_DYNAMIC_CPP_STEPS})
         add_executable(e2e-steps EXCLUDE_FROM_ALL ${CUKE_DYNAMIC_CPP_STEPS})
+        # Mark this file as generated so it isn't required at CMake generation time (it is necessary when the target gets built though)
+        set_source_files_properties(${CUKE_DYNAMIC_CPP_STEPS} PROPERTIES GENERATED TRUE)
         target_link_libraries(e2e-steps ${CUKE_LIBRARIES})
 
         set(CUKE_COMPILE_DYNAMIC_CPP_STEPS '"${CMAKE_COMMAND}" --build "${CMAKE_BINARY_DIR}" --target e2e-steps')