Disable bootstrap for stage0

[vertexclique]

Amanieu mentioned that stage0 build should exclude TME for Aarch64 in here: rust-lang/rust#72749 (comment)

r? @Amanieu

[Amanieu]

You also need to #[cfg] out the use line below.

[vertexclique]

Yup, forgot that.

[Mark-Simulacrum]

Before we land this -- I want to be sure that I'm following correctly -- this will not break when we update the bootstrap compiler, right? It'll just retain less functionality? Historically having cfg(bootstrap) outside of rust-lang/rust proper is pretty painful so it would be good to avoid this if possible (say, by waiting ~1 week after bootstrap is bumped in rust-lang/rust).

[Amanieu]

Actually I think the issue is not due to stage0. Looking at the CI logs it seems that rustdoc is failing because it doesn't recognize the "tme" target feature. Why is stage0 rustdoc used here?

[Amanieu]

Sorry it seems I was wrong about the issue. I'll close this and we can continue discussion in rust-lang/rust#72749.

[Amanieu]

Reopening as per rust-lang/rust#72749 (comment)

[Amanieu]

Please update your submodule in the other PR to include this.