Fix RWC Runner (#10420)

* Use /// <reference types

* Don't report an errors if it comes from lib.d.ts

src/harness/rwcRunner.ts

@@ -198,7 +198,8 @@ namespace RWC {
                     }
                     // Do not include the library in the baselines to avoid noise
                     const baselineFiles = inputFiles.concat(otherFiles).filter(f => !Harness.isDefaultLibraryFile(f.unitName));
-                    return Harness.Compiler.getErrorBaseline(baselineFiles, compilerResult.errors);
+                    const errors = compilerResult.errors.filter(e => !Harness.isDefaultLibraryFile(e.file.fileName));
+                    return Harness.Compiler.getErrorBaseline(baselineFiles, errors);
                 }, false, baselineOpts);
             });