soh-torch and soh-o2r-packer both exist to turn assets into archives, so
they sit better beside the assets they read than at the repo root.
Nothing tangled: both targets are declared in the root CMakeLists with
explicit paths rather than add_subdirectory, and soh/CMakeLists.txt globs
only include/, soh/ and src/, so sources under assets/ aren't swept into
the soh target.
briaguya