[BE] Remind users to update submodule

Summary: As titled. This adds messages when we suspect the user forgot
to update git submodule or cleanup the CMake cache.

Test Plan: See the following error messages

Reviewers:

Subscribers:

Tasks:

Tags:

ghstack-source-id: 6236566b68a6df7d485ef74566d53c67a771eace
Pull Request resolved: https://github.com/pytorch/executorch/pull/8203

Co-authored-by: Mengwei Liu <larryliu@meta.com>