Controlling UF‌O instance output from -m seems impossible

When compiling a single instance to UFO from a designspace using `-m .designspace -i '' -o ufo --output-path .ufo`, the resulting instance UFO does not end up where it is supposed to or with the right name. Instead it ends up in an automatically named UFO in the "instance_ufos" directory next to wherever the source was.

Any attempt to fix this with other arguments seems to be stifled: `--instance-dir` says it cannot be used with `-m`, and `--output-dir` has no affect either.