Can we move mimalloc.cpp to a separate directory?

Looks like mimalloc.cpp was added recently to pull in new and delete symbols. For projects that already depend on mimalloc and pull in these symbols it creates a conflict. A bunch of effort is needed in each build system now to filter out mimalloc.cpp from glob operations. Can we instead move it to its own directory to make filtering it out easier? e.g. sources/mimalloc/mimalloc.cpp or sources/optional/mimalloc.cpp?

Start by locating sources/mimalloc.cpp and the build-system rules or glob operations that include it. Compare the proposed directory locations and trace how the file is selected by each build path. Done means the file is separated as requested and projects using source globs no longer need to filter it out.

Written by the indexing model from the issue text.