Auto merge of #137836 - madsmtm:openwrt-target-vendor, r=jieyouxu

Set `target_vendor = "openwrt"` on `mips64-openwrt-linux-musl`

OpenWRT is a Linux distribution for embedded network devices. The target name contains `openwrt`, so we should set `cfg(target_vendor = "openwrt")`.

This is similar to what other Linux distributions do (the only one in-tree is `x86_64-unikraft-linux-musl`, but that sets `target_vendor = "unikraft"`).

Motivation: To make correctly [parsing target names](https://github.com/rust-lang/cc-rs/pull/1413) simpler.

Fixes https://github.com/rust-lang/rust/issues/131165.

CC target maintainer `@Itus-Shield`

compiler/rustc_target/src/spec/targets/mips64_openwrt_linux_musl.rs

@@ -23,6 +23,7 @@ pub(crate) fn target() -> Target {
         data_layout: "E-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128".into(),
         arch: "mips64".into(),
         options: TargetOptions {
+            vendor: "openwrt".into(),
             abi: "abi64".into(),
             endian: Endian::Big,
             mcount: "_mcount".into(),