Fix wrong help message left in rust-lang#31368

Author: JohanLorenzo

src/librustc/session/config.rs

@@ -510,7 +510,7 @@ options! {CodegenOptions, CodegenSetter, basic_codegen_options,
     link_args: Option<Vec<String>> = (None, parse_opt_list,
         "extra arguments to pass to the linker (space separated)"),
     link_dead_code: bool = (false, parse_bool,
-        "let the linker strip dead coded (turning it on can be used for code coverage)"),
+        "don't let linker strip dead code (turning it on can be used for code coverage)"),
     lto: bool = (false, parse_bool,
         "perform LLVM link-time optimizations"),
     target_cpu: Option<String> = (None, parse_opt_string,