build: cmake walks through entire ns-3-dev directory?

If a user has a directory that stores something (e.g., simulation results) inside the ns-3-dev root directory, configuring ns3 (e.g., CXX="clang++" ./ns3 configure --build-profile=release) will take forever because it seems that cmake/ns3 walks through entire ns-3-dev directory including the sub-directory that stores the results. I did not have such issue with waf. Is this the expected behavior with cmake (ns3 script)?