We have been using directories prefixed with name 'build_' to indicate that it's the directory to build inside of.
The 'build_cmake' directory contains CMake source code for the build system and should generally not be used as a build directory. This could be problematic as building inside 'build_cmake' could clobber and delete sources that are needed to execute the build.
Rename 'build_cmake' directory to avoid potential confusion (A couple of open source projects that need a separate directory for CMake scripts often just call the directory 'cmake' or 'CMake'). We will also need to make sure any paths with 'build_cmake' are also updated.