refactor(compiler-cli): ensure compatibility with noImplicitOverride (#42512)

Adds the `override` keyword to the `compiler-cli` sources to ensure
compatibility with `noImplicitOverride`.

PR Close #42512

packages/compiler-cli/linker/src/file_linker/emit_scopes/iife_emit_scope.ts

@@ -30,7 +30,7 @@ export class IifeEmitScope<TStatement, TExpression> extends EmitScope<TStatement
    * Wraps the output from `EmitScope.translateDefinition()` and `EmitScope.getConstantStatements()`
    * in an IIFE.
    */
-  translateDefinition(definition: o.Expression): TExpression {
+  override translateDefinition(definition: o.Expression): TExpression {
     const constantStatements = super.getConstantStatements();
 
     const returnStatement =
@@ -44,7 +44,7 @@ export class IifeEmitScope<TStatement, TExpression> extends EmitScope<TStatement
    * It is not valid to call this method, since there will be no shared constant statements - they
    * are already emitted in the IIFE alongside the translated definition.
    */
-  getConstantStatements(): TStatement[] {
+  override getConstantStatements(): TStatement[] {
     throw new Error('BUG - IifeEmitScope should not expose any constant statements');
   }
 }