fix(@schematics/angular): use app root to set server paths in options

Author: alan-agius4

packages/schematics/angular/migrations/update-6/index.ts

@@ -536,8 +536,8 @@ function extractProjectsConfig(
       if (serverApp) {
         const serverOptions: JsonObject = {
           outputPath: serverApp.outDir || defaults.serverOutDir,
-          main: serverApp.main || defaults.serverMain,
-          tsConfig: serverApp.tsconfig || defaults.serverTsConfig,
+          main: `${appRoot}/${serverApp.main || defaults.serverMain}`,
+          tsConfig: `${appRoot}/${serverApp.tsconfig || defaults.serverTsConfig}`,
         };
         const serverTarget: JsonObject = {
           builder: '@angular-devkit/build-angular:server',

packages/schematics/angular/migrations/update-6/index_spec.ts

@@ -992,8 +992,8 @@ describe('Migration to v6', () => {
       expect(target).toBeDefined();
       expect(target.builder).toEqual('@angular-devkit/build-angular:server');
       expect(target.options.outputPath).toEqual('dist/server');
-      expect(target.options.main).toEqual('main.server.ts');
-      expect(target.options.tsConfig).toEqual('tsconfig.server.json');
+      expect(target.options.main).toEqual('src/main.server.ts');
+      expect(target.options.tsConfig).toEqual('src/tsconfig.server.json');
     });
   });
 });