normalize use of backticks for compiler messages in librustc_codegen

https://github.com/rust-lang/rust/issues/60532

src/test/ui/crate-name-mismatch.rs

@@ -1,6 +1,6 @@
 // compile-flags: --crate-name foo
 
 #![crate_name = "bar"]
-//~^ ERROR: --crate-name and #[crate_name] are required to match, but `foo` != `bar`
+//~^ ERROR: `--crate-name` and `#[crate_name]` are required to match, but `foo` != `bar`
 
 fn main() {}

src/test/ui/crate-name-mismatch.stderr

@@ -1,4 +1,4 @@
-error: --crate-name and #[crate_name] are required to match, but `foo` != `bar`
+error: `--crate-name` and `#[crate_name]` are required to match, but `foo` != `bar`
   --> $DIR/crate-name-mismatch.rs:3:1
    |
 LL | #![crate_name = "bar"]

src/test/ui/duplicate/dupe-symbols-7.stderr

@@ -4,7 +4,7 @@ error: entry symbol `main` defined multiple times
 LL | fn main(){}
    | ^^^^^^^^^^^
    |
-   = help: did you use #[no_mangle] on `fn main`? Use #[start] instead
+   = help: did you use `#[no_mangle]` on `fn main`? Use `#[start]` instead
 
 error: aborting due to previous error