Support no_std in Prost toolchain

[fionera]

No description provided.

[UebelAndre]

Thanks! Just one minor request!

[UebelAndre]

One last nit and I think you can delete rust_prost.md since docs are now generated directly from the bzl source file. Devs no longer need to render them and add them to their PRs 😄

[UebelAndre]

Thanks!

[UebelAndre]

Actually, is there some sort of integration test you can add that uses this new flag?

[fionera]

If you give me an example, I could take a look

[UebelAndre]

If you give me an example, I could take a look

Like any of the cases here: https://github.com/bazelbuild/rules_rust/tree/5226882efee4c3f1f2b68940b06fad9ad070f8b1/extensions/prost/private/tests

if there’s a single test that that uses use_no_std then there is some regression testing to know if a future change breaks this feature.

[UebelAndre]

Like any of the cases here: https://github.com/bazelbuild/rules_rust/tree/5226882efee4c3f1f2b68940b06fad9ad070f8b1/extensions/prost/private/tests

if there’s a single test that that uses use_no_std then there is some regression testing to know if a future change breaks this feature.

Let me know if you still have questions! Happy to get this merged but it'll be super helpful down the line to have at least 1 regression test.