Promote `armv7-unknown-linux-musleabihf` to tier 2 with host tools

[alex]

Proposal

I would like to propose promoting the armv7-unknown-linux-musleabihf target from Tier 2 to Tier 2 with Host Tools.

Tier 2 with Host Tools Requirements

The host tools must have direct value to people other than the target's maintainers

ARMv7 remains a widely used platform and musl is very commonly used in container builds, thus I expect there to be many users at that intersection.

My personal motivation is to be able to produce binary artifacts for Python packages using Rust for the "musllinux" on ARMv7 ABI.

There must be a reasonable expectation that the host tools will be used

I am specifically motivated by the desire to use them to ship production builds :-) For the previous described reasons, I'm sure others will as well.

The host tools must build and run reliably in CI

I expect host tools to build reliably given:

• The target already builds successfully as Tier 2
• ARMv7 code generation is mature and stable
• musl provides a stable compilation environment

A draft PR exists at rust-lang/rust#142538

Building host tools for the target must not take substantially longer than building host tools for other targets

Host tool compilation should be comparable to other ARMv7 targets.

The host tools must provide a substantively similar experience as on other targets

This is a standard musl linux target, it should be consistent with other platforms

Process

The main points of the Major Change Process are as follows:

• File an issue describing the proposal.
• A compiler team member or contributor who is knowledgeable in the area can second by writing @rustbot second.
  • Finding a "second" suffices for internal changes. If however, you are proposing a new public-facing feature, such as a -C flag, then full team check-off is required.
  • Compiler team members can initiate a check-off via @rfcbot fcp merge on either the MCP or the PR.
• Once an MCP is seconded, the Final Comment Period begins. If no objections are raised after 10 days, the MCP is considered approved.

You can read more about Major Change Proposals on forge.

Caution

Concerns (1 active)

• lack-of-maintainers

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[rustbot]

Important

This issue is not meant to be used for technical discussion. There is a Zulip stream for that.
Use this issue to leave procedural comments, such as volunteering to review, indicating that you second the proposal (or third, etc), or raising a concern that you would like to be addressed.

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cc @rust-lang/compiler

[alex]

The initial feedback from Zulip here was: this target was grandfathered into tier 2, and thus probably needs review for many of the traditional tier 2 factors. Most significantly, the requirement for multiple dedicated maintainers. I personally lack the expertise (in both armv7 and musl) to volunteer for that, which I think leaves this MCP at an impasse.

[apiraino]

@rustbot concern lack-of-maintainers

From Zulip: this target was grandfathered and it seems to be lacking actual maintainers. This could be a concern if we promote this target futher up in out support chain