Lint against untranslatable diagnostics in rustc_codegen_gcc

Author: ellishg

compiler/rustc_codegen_gcc/src/lib.rs

@@ -18,6 +18,8 @@
 #![recursion_limit="256"]
 #![warn(rust_2018_idioms)]
 #![warn(unused_lifetimes)]
+#![deny(rustc::untranslatable_diagnostic)]
+#![deny(rustc::diagnostic_outside_of_impl)]
 
 extern crate rustc_apfloat;
 extern crate rustc_ast;