[MISched] Fix non-debug builds.

As reported in https://github.com/llvm/llvm-project/issues/63225, we
need to make sure we can use the `&operator<<` on instances of the
`ResourceSegments` class for builds that set `NDEBUG`.

Reviewed By: sylvestre.ledru

Differential Revision: https://reviews.llvm.org/D152817