Rollup merge of #87553 - bjorn3:fix_hotplug_codegen_version, r=wesleywiser

Fix typo in rustc_driver::version

This caused rustc `-Zcodegen-backend=foo.so -vV` to look for `oo.so` instead of `foo.so`

compiler/rustc_driver/src/lib.rs

@@ -764,13 +764,7 @@ fn unw(x: Option<&str>) -> &str {
         println!("release: {}", unw(util::release_str()));
 
         let debug_flags = matches.opt_strs("Z");
-        let backend_name = debug_flags.iter().find_map(|x| {
-            if x.starts_with("codegen-backend=") {
-                Some(&x["codegen-backends=".len()..])
-            } else {
-                None
-            }
-        });
+        let backend_name = debug_flags.iter().find_map(|x| x.strip_prefix("codegen-backend="));
         get_codegen_backend(&None, backend_name).print_version();
     }
 }