Remove EarlyDiagCtxt::abort_if_errors.

Its one use isn't necessary, because it's not possible for errors to
have been emitted at that point.

compiler/rustc_driver_impl/src/lib.rs

@@ -349,11 +349,10 @@ fn run_compiler(
         },
     };
 
-    callbacks.config(&mut config);
-
-    default_early_dcx.abort_if_errors();
     drop(default_early_dcx);
 
+    callbacks.config(&mut config);
+
     interface::run_compiler(config, |compiler| {
         let sess = &compiler.sess;
         let codegen_backend = &*compiler.codegen_backend;