Build Cache doesn't recognize metadata file changes

### What happened?

The build cache doesn't appear to be catching changes to CCPP metadata files in the source code. This may be related to issue #239.

### What are the steps to reproduce the bug?

Modify a metadata file in the CAM-SIMA source code after running `preview_namelists` or `case_build` for a particular case, and then try re-building the model or namelists again. You should notice that the build cache won't catch the modified metadata file and thus won't update the auto-generated CCPP caps.

### What CAM-SIMA hash were you using?

7d299b6

### What machine were you running CAM-SIMA on?

CISL machine (e.g. cheyenne)

### What compiler were you using?

GNU

### Path to a case directory, if applicable

_No response_

### Will you be addressing this bug yourself?

Any Software Engineer can do this

### Extra info

This particular problem can currently be resolved by running `./case_build --clean-all` after modifying a metadata file to force the build system to regenerate the caps.