Fix lint

Author: weswigham

src/harness/externalCompileRunner.ts

@@ -27,6 +27,7 @@ abstract class ExternalCompileRunnerBase extends RunnerBase {
         // Read in and evaluate the test list
         const testList = this.tests && this.tests.length ? this.tests : this.enumerateTestFiles();
 
+        // tslint:disable-next-line:no-this-assignment
         const cls = this;
         describe(`${this.kind()} code samples`, function(this: Mocha.ISuiteCallbackContext) {
             this.timeout(600_000); // 10 minutes