Don't leak deps from rust_proc_macro

[scentini]

Dependencies of a rust_proc_macro shouldn't propagate to the libraries depending on the rust_proc_macro target.

We ran into this issue in a complex internal build that involved transitions - the final rust_ilbrary had the same crate as input twice, once from the regular exec configuration and once from the transition configuration. The error presented itself as

error[E0523]: found two different crates with name X that are not distinguished by differing -C metadata. This will result in symbol conflicts between the two.

[UebelAndre]

Whenever either one of you have time, would one of you be able to add some details about the change here? I'm most curious to know if you ran into an issue and if there's a callstack that could be posted here so curious users can find something was fixed.

[scentini]

Hey @UebelAndre, I updated the description, PTAL.

[UebelAndre]

Hey @UebelAndre, I updated the description, PTAL.

Thank you!