Angular/Typescript remove unused code at compile time

Question

I'm using Angular 9 and I have some code like this:

(features.ts, autogenerated:)
// AUTO-GENERTATED FILE. DO NOT EDIT!
export const Features = {
  // Whether to reveal our Secret New Feature to the world
  ENABLE_SECRET_FEATURE: 1
};

(mycode.ts, app code)
import { Features } from 'generated/features.ts';

function doSomething() {
  if (Features.ENABLE_SECRET_FEATURE) {
    doAIBlockChainARThing();
  } else {
    doSomeBoringOldCRUDThing();
  }
}

I'd like the code emitted to be EITHER

function doSomething() {
    doAIBlockChainARThing();
}

OR

function doSomething() {
    doSomeBoringOldCRUDThing();
}

but not both.

Is there an invocation of ng build that would make this happen? I know uglify can sort of do this and Closure Compiler certainly can. My current invocation is: ng build --aot=true --stats-json --buildOptimizer=true --optimization=true --prod

UPDATE:

After some experimentation I have discovered that the terser settings in Angular prod builds do what I want if I have code like:

const SECRET_FEATURE = true;
if (SECRET_FEATURE) {
  // code here is emitted
} else {
  // code here is NOT emitted
}

However if I try to do something like:

import {SECRET_FEATURE} from 'my-features';

if (SECRET_FEATURE) { // this conditional is emitted
  // this code is emitted
} else {
  // this code is also emitted
}