Add support for OpenHarmony

[Amanieu]

This PR adds support for OpenHarmony targets:

• aarch64-linux-ohos
• arm-linux-ohos

Compiler team MCP: rust-lang/compiler-team#568

OpenHarmony uses a fork of musl with minor modifications, so most of the code is shared with other musl targets. Additionally, although OpenHarmony uses musl 1.2, it is still ABI-compatible with musl 1.1 so the existing bindings should continue to work until #3068 is merged.

A PR to add the targets to rustc will follow after this is merged.

[rustbot]

r? @JohnTitor

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[notgull]

Out of curiosity, does OpenHarmony provide a new polling system, or does it just use Epoll like Linux does?

[Amanieu]

These OpenHarmony targets run on top of the Linux kernel and therefore support the same standard mechanisms that Linux provides. However OpenHarmony also supports running on embedded devices & microcontrollers with a custom kernel (LiteOS), but these targets are not currently supported in this PR.

[JohnTitor]

Thanks!
@bors r+

[bors]

📌 Commit 3f5128e has been approved by JohnTitor

It is now in the queue for this repository.

[bors]

⌛ Testing commit 3f5128e with merge da4f8f8...

[bors]

☀️ Test successful - checks-actions, checks-cirrus-freebsd-12, checks-cirrus-freebsd-13, checks-cirrus-freebsd-14
Approved by: JohnTitor
Pushing da4f8f8 to master...

[bors]

☀️ Test successful - checks-actions, checks-cirrus-freebsd-12, checks-cirrus-freebsd-13, checks-cirrus-freebsd-14
Approved by: JohnTitor
Pushing da4f8f8 to master...

[bors]

👀 Test was successful, but fast-forwarding failed: 422 Changes must be made through a pull request.