Implement the MCP 932: Promote riscv64a23-unknown-linux-gnu to Tier 2

[ZhongyaoChen]

Implement the MCP 932: Promote riscv64a23-unknown-linux-gnu to Tier 2 without host tools.

Closes #148353.

Changes:

• Update target tier from 3 to 2 in target specification
• Update platform documentation
• Add CI/CD support for automatic building and distribution via rustup

r? jieyouxu
cc @davidtwco @Noratrieb

[rustbot]

Some changes occurred in src/doc/rustc/src/platform-support

cc @Noratrieb

These commits modify compiler targets.
(See the Target Tier Policy.)

[jieyouxu]

Thanks

View changes since this review

[jieyouxu]

@bors r+

[bors]

📌 Commit 1af9b63 has been approved by jieyouxu

It is now in the queue for this repository.

[jieyouxu]

Actually, this can affect CI duration so
@bors rollup=never

[bors]

⌛ Testing commit 1af9b63 with merge 6647be9...

[bors]

☀️ Test successful - checks-actions
Approved by: jieyouxu
Pushing 6647be9 to master...

[github-actions]

What is this?

This is an experimental post-merge analysis report that shows differences in test outcomes between the merged PR and its parent PR.

Comparing 86b95eb (parent) -> 6647be9 (this PR)

Test differences

Show 3 test diffs

3 doctest diffs were found. These are ignored, as they are noisy.

Test dashboard

Run

cargo run --manifest-path src/ci/citool/Cargo.toml -- \
    test-dashboard 6647be93640686a2a443a49f15c3390b68c8b5dd --output-dir test-dashboard

And then open test-dashboard/index.html in your browser to see an overview of all executed tests.

Job duration changes

1. pr-check-1: 1361.8s -> 1704.2s (+25.1%)
2. x86_64-gnu-gcc: 2797.5s -> 3423.9s (+22.4%)
3. aarch64-apple: 8804.5s -> 10622.4s (+20.6%)
4. i686-gnu-2: 5426.7s -> 6309.2s (+16.3%)
5. dist-x86_64-apple: 7449.1s -> 8637.5s (+16.0%)
6. aarch64-gnu-llvm-20-2: 2141.9s -> 2469.6s (+15.3%)
7. x86_64-gnu-llvm-20: 2491.1s -> 2862.3s (+14.9%)
8. aarch64-gnu: 6353.0s -> 7252.5s (+14.2%)
9. aarch64-gnu-llvm-20-1: 3458.8s -> 3894.9s (+12.6%)
10. x86_64-gnu-llvm-21-1: 3273.3s -> 3664.4s (+11.9%)

How to interpret the job duration changes?

Job durations can vary a lot, based on the actual runner instance
that executed the job, system noise, invalidated caches, etc. The table above is provided
mostly for t-infra members, for simpler debugging of potential CI slow-downs.

[rust-timer]

Finished benchmarking commit (6647be9): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

This benchmark run did not return any relevant results for this metric.

Max RSS (memory usage)

Results (primary -1.4%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-1.4%	[-1.4%, -1.4%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-1.4%	[-1.4%, -1.4%]	1

Cycles

This benchmark run did not return any relevant results for this metric.

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 476.643s -> 475.519s (-0.24%)
Artifact size: 391.27 MiB -> 391.32 MiB (0.01%)