Can not enable scss build at angular 6.0.1

[13812453806]

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[ ] feature request
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Current behavior
I want enable scss
Reference https://github.com/mgechev/angular-seed/wiki/Working-with-SASS

I create src/client/scss directory
add main.scss
body {
background-color: red;
}

in project.config.ts
add this.ENABLE_SCSS = true;

same step and scss directory and file

exec npm run build.prod.aot
at angular 5.2.9 commit id df278b8
dist/prod/css/main.css generate ok
background-color: red; Take effect

but at angular 6.0.1 commit id b43ccde
dist/prod/css/main.css not include background-color: red; css style no any effect

two commit id build success, no any build fail

Expected behavior
two commit id build success, include background-color: red; style css

Minimal reproduction of the problem with instructions
git clone code
git checkout b43ccde
create src/client/scss directory
add main.scss
body {
background-color: red;
}

in project.config.ts
add this.ENABLE_SCSS = true;

exec npm run build.prod.aot

check background-color: red; not effect

What is the motivation / use case for changing the behavior?
enable scss build

Please tell us about your environment:
Operating system : Mac osx 10.11.6
IDE: VS code 1.24.1
package manager: https://registry.npmjs.org/ npm install
HTTP server: openresty/1.9.7.5

• Angular Seed Version: aaaaf75
  Angular seed version df278b87750a5dd17ec24f42aa84a52c34ad18e6 OK
  Angular seed version b43ccde9f2126cab03d91dd70387d67676db1b45 FAIL

• Node: node --version =
  node --version = v9.10.1