[Rust] loongarch64-unknown-linux-musl target

[heiher]

由于当前musl loongarch64 port的补丁还没有进入上游，Rust loongarch64-unknown-linux-musl target的上游工作暂不可开展。创建一个讨论贴用于汇总早期工作，方便沟通互动和暴露问题。

• musl v8: https://github.com/heiher/musl/commits/loongarch64 (已进上游)
• rust loongarch64-linux-musl: https://github.com/heiher/rust/commits/musl
• rust libc: https://github.com/heiher/libc/commits/musl
• rust compiler-builtins: https://github.com/heiher/compiler-builtins/commits/musl

[heiher]

Musl 1.2.5发布，已包含 LoongArch 支持： https://git.musl-libc.org/cgit/musl/log/?h=v1.2.5

[heiher]

Rust loongarch64-unknown-linux-musl 开始提交：

compiler-builtins: rust-lang/compiler-builtins#579
libc: rust-lang/libc#3605 rust-lang/libc#3606
rust: rust-lang/rust#121832

crosstool-ng: crosstool-ng/crosstool-ng#2118 crosstool-ng/crosstool-ng#2119 crosstool-ng/crosstool-ng#2120

[xen0n]

rust-lang/rust#122592

[heiher]

Tracking in rust-lang/rust#122592