CMakeLists.txt: Change cleaning commands to respect out of source builds.
CMakeLists.txt: Change cleaning commands to respect out of source builds.

nanshe-org/rank_filter,DudLab/rank_filter,DudLab/rank_filter,DudLab/rank_filter,nanshe-org/rank_filter,jakirkham/rank_filter,jakirkham/rank_filter,nanshe-org/rank_filter,jakirkham/rank_filter