fix(@schematics/angular): infer main server file name from main option

Author: alan-agius4

packages/schematics/angular/universal/files/root/__tsconfigFileName__.json.template

@@ -5,7 +5,7 @@
     "module": "commonjs"
   },
   "files": [
-    "src/main.server.ts"
+    "src/<%= stripTsExtension(main) %>.ts"
   ],
   "angularCompilerOptions": {
     "entryModule": "./<%= rootInSrc ? '' : 'src/' %><%= appDir %>/<%= stripTsExtension(rootModuleFileName) %>#<%= rootModuleClassName %>"

packages/schematics/angular/universal/index.ts

@@ -49,12 +49,13 @@ function updateConfigFile(options: UniversalOptions, tsConfigDirectory: Path): R
         fileReplacements = buildTarget.configurations.production.fileReplacements;
       }
 
+      const mainPath = options.main as string;
       clientProject.targets.add({
         name: 'server',
         builder: Builders.Server,
         options: {
           outputPath: `dist/${options.clientProject}-server`,
-          main: join(normalize(clientProject.root), 'src/main.server.ts'),
+          main: join(normalize(clientProject.root), 'src', mainPath.endsWith('.ts') ? mainPath : mainPath + '.ts'),
           tsConfig: join(tsConfigDirectory, `${options.tsconfigFileName}.json`),
         },
         configurations: {