Support for a new `wasm32-wali-linux-musl` Tier-3 target

[arjunr2]

Proposal

Adding a new target -- wasm32-wali-linux-musl -- to the compiler can target the WebAssembly Linux Interface.
Preliminary support is already implemented for this in the fork here, and involves minimal changes, primarily

1. A new target spec for wasm32_wali_linux_musl that bridges linux options with supported wasm options. Right now, since there is no canonical Linux ABI for Wasm, we use wali in the vendor field.
2. Patches to stdarch, cc, and libc
3. Minimal FFI support for the target

Mentors or Reviewers

@alexcrichton pointed me to this and might be helpful in reviewing this effort

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.

Comments

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.

[rustbot]

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.

Concerns or objections to the proposal should be discussed on Zulip and formally registered here by adding a comment with the following syntax:

@rustbot concern reason-for-concern 
<description of the concern> 

Concerns can be lifted with:

@rustbot resolve reason-for-concern 

See documentation at https://forge.rust-lang.org

cc @rust-lang/compiler @rust-lang/compiler-contributors

[workingjubilee]

Let the prophecy be fulfilled:

• Wario
• Waluigi
• Walinux

@rustbot second

[apiraino]

@rustbot label -final-comment-period +major-change-accepted