compile rust for mips3, see https://github.com/rust-lang/rust/issues/88942

mips3.patch

diff --git a/compiler/rustc_target/src/spec/targets/mips64el_unknown_linux_gnuabi64.rs b/compiler/rustc_target/src/spec/targets/mips64el_unknown_linux_gnuabi64.rs
index 515473fbabc..fa3c6875964 100644
--- a/compiler/rustc_target/src/spec/targets/mips64el_unknown_linux_gnuabi64.rs
+++ b/compiler/rustc_target/src/spec/targets/mips64el_unknown_linux_gnuabi64.rs
@@ -15,8 +15,8 @@ pub fn target() -> Target {
         options: TargetOptions {
             abi: "abi64".into(),
             // NOTE(mips64r2) matches C toolchain
-            cpu: "mips64r2".into(),
-            features: "+mips64r2,+xgot".into(),
+            cpu: "mips3".into(),
+            features: "+mips3,+xgot".into(),
             max_atomic_width: Some(64),
             mcount: "_mcount".into(),