Auto merge of #87449 - matthiaskrgr:clippyy_v2, r=nagisa

more clippy::complexity fixes

(also a couple of clippy::perf fixes)

compiler/rustc_target/src/spec/mod.rs

@@ -2018,7 +2018,7 @@ impl Target {
 
         if base.is_builtin {
             // This can cause unfortunate ICEs later down the line.
-            return Err(format!("may not set is_builtin for targets not built-in"));
+            return Err("may not set is_builtin for targets not built-in".to_string());
         }
         // Each field should have been read using `Json::remove_key` so any keys remaining are unused.
         let remaining_keys = obj.as_object().ok_or("Expected JSON object for target")?.keys();