[9.0.1] ng build file replacements don't work after update to v9

[SansDK]

🐞 Bug report

Command (mark with an x)

• new
• build
• serve
• test
• e2e
• generate
• add
• update
• lint
• xi18n
• run
• config
• help
• version
• doc

Is this a regression?

Yes, the previous version in which this bug was not present was the latest angular-cli v8 release (v8.3.25)

Description

I have a `config.js` file which has some settings in it, and it should be replaced by a production `config.js` when performing a production build.

This worked fine, until I upgraded to angular-cli v9. I don't get errors or warnings, but the config.js in the dist folder after building is the non-prod version, while I would expect the prod version.

In my angular.json file, I have the following:

...
"configurations": {
  "production": {
    "fileReplacements": [
      {
        "replace": "src/config.js",
        "with": "src/prod/config.js"
      }
    ]
  }
}

The command ng build --prod doesn't cause the file to be replaced, and neither does ng build --configuration=production.

🔬 Minimal Reproduction

1. Create a new project with the latest Angular v8 & Angular CLI v8 release.
2. Add the file replacement config & files like above.
3. Run ng build --prod. File replacement works now.
4. Update to Angular & Angular CLI 9 (run ng update @angular/core @angular/cli)
5. Run ng build --prod again. The file doesn't get replaced anymore (original config.js will be present in the dist folder). ❌

🌍 Your Environment

Angular CLI: 9.0.1
Node: 13.0.1
OS: win32 x64

Angular: 9.0.0
... animations, cdk, common, compiler, compiler-cli, core, forms
... language-service, material, platform-browser
... platform-browser-dynamic, router
Ivy Workspace: Yes

Package                           Version
-----------------------------------------------------------
@angular-devkit/architect         0.900.1
@angular-devkit/build-angular     0.900.1
@angular-devkit/build-optimizer   0.900.1
@angular-devkit/build-webpack     0.900.1
@angular-devkit/core              9.0.1
@angular-devkit/schematics        9.0.1
@angular/cli                      9.0.1
@ngtools/webpack                  9.0.1
@schematics/angular               9.0.1
@schematics/update                0.900.1
rxjs                              6.5.4
typescript                        3.7.5
webpack                           4.41.2

[alan-agius4]

Duplicate of #16779

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