_                      _                 ____ _     ___
    / \   _ __   __ _ _   _| | __ _ _ __     / ___| |   |_ _|
   / △ \ | '_ \ / _` | | | | |/ _` | '__|   | |   | |    | |
  / ___ \| | | | (_| | |_| | | (_| | |      | |___| |___ | |
 /_/   \_\_| |_|\__, |\__,_|_|\__,_|_|       \____|_____|___|
                |___/


Angular CLI: 6.0.1
Node: 10.0.0
OS: linux x64
Angular: 6.0.1
... animations, cli, common, compiler, compiler-cli, core, forms
... http, language-service, platform-browser
... platform-browser-dynamic, router

Package                           Version
-----------------------------------------------------------
@angular-devkit/architect         0.6.1
@angular-devkit/build-angular     0.6.1
@angular-devkit/build-optimizer   0.6.1
@angular-devkit/core              0.6.1
@angular-devkit/schematics        0.6.1
@ngtools/webpack                  6.0.1
@schematics/angular               0.6.1
@schematics/update                0.6.1
rxjs                              6.1.0
typescript                        2.7.2
webpack                           4.6.0

node --version
v10.0.0
npm --version
5.6.0

Linux localhost.localdomain 3.10.0-514.16.1.el7.x86_64 #1 SMP Wed Apr 12 15:04:24 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux

npm install -g @angular/cli
ng new my-dream-app
cd my-dream-app

Create an empty file _variables.scss in src/.

Add the following to _variables.scss:

$fa-font-path : '../node_modules/font-awesome/fonts';
In styles.scss add the following:

@import 'variables';
@import '../node_modules/font-awesome/scss/font-awesome';

ERROR in ./src/styles.css (./node_modules/raw-loader!./node_modules/postcss-loader/lib??embedded!./src/styles.css)
Module build failed: Error: Can't resolve 'variables' in '/var/www/mydream-app/src'
    at doResolve (/var/www/mydream-app/node_modules/enhanced-resolve/lib/Resolver.js:177:19)
    at hook.callAsync (/var/www/mydream-app/node_modules/enhanced-resolve/lib/Resolver.js:232:5)
    at _fn0 (eval at create (/var/www/mydream-app/node_modules/tapable/lib/HookCodeFactory.js:24:12), <anonymous>:15:1)
    at resolver.doResolve (/var/www/mydream-app/node_modules/enhanced-resolve/lib/UnsafeCachePlugin.js:37:5)
    at hook.callAsync (/var/www/mydream-app/node_modules/enhanced-resolve/lib/Resolver.js:232:5)
    at _fn0 (eval at create (/var/www/mydream-app/node_modules/tapable/lib/HookCodeFactory.js:24:12), <anonymous>:15:1)
    at hook.callAsync (/var/www/mydream-app/node_modules/enhanced-resolve/lib/Resolver.js:232:5)
    at _fn0 (eval at create (/var/www/mydream-app/node_modules/tapable/lib/HookCodeFactory.js:24:12), <anonymous>:12:1)
    at resolver.doResolve (/var/www/mydream-app/node_modules/enhanced-resolve/lib/DescriptionFilePlugin.js:42:38)
    at hook.callAsync (/var/www/mydream-app/node_modules/enhanced-resolve/lib/Resolver.js:232:5)
    at _fn5 (eval at create (/var/www/mydream-app/node_modules/tapable/lib/HookCodeFactory.js:24:12), <anonymous>:57:1)
    at resolver.doResolve (/var/www/mydream-app/node_modules/enhanced-resolve/lib/ModuleKindPlugin.js:23:37)
    at hook.callAsync (/var/www/mydream-app/node_modules/enhanced-resolve/lib/Resolver.js:232:5)
    at _fn0 (eval at create (/var/www/mydream-app/node_modules/tapable/lib/HookCodeFactory.js:24:12), <anonymous>:15:1)
    at hook.callAsync (/var/www/mydream-app/node_modules/enhanced-resolve/lib/Resolver.js:232:5)
    at _fn1 (eval at create (/var/www/mydream-app/node_modules/tapable/lib/HookCodeFactory.js:24:12), <anonymous>:24:1)

Make sure that angular.json is using styles.**scss**
// in angular.json
"build": {
  "options": {
    "styles": [
      "styles.scss"
    ],
  }
}