MSVC examples cannot be exported with out-dir

[ehuss]

If a project has an example binary, normally --out-dir will export those examples to the output directory. However, as of #7400, examples are no longer exported for MSVC targets.

This is because the metadata hash has been removed from the filename. The out-dir linking code relies on the hardlink field to know which files to link. Since the example no longer is hard linked, it is no longer exported.

I think somehow calc_outputs_rustc should use a different mechanism to determine which files to export.

This is relevant to the collision_export test.