fix(@angular-devkit/build-angular): provide better error message when server option is required but missing

This improves the error message when the server entry-point is required but missing

Closes #27251

(cherry picked from commit 1034bb1)

Author: alan-agius4

packages/angular_devkit/build_angular/src/builders/application/options.ts

@@ -238,7 +238,7 @@ export async function normalizeOptions(
   if (options.server) {
     serverEntryPoint = path.join(workspaceRoot, options.server);
   } else if (options.server === '') {
-    throw new Error('`server` option cannot be an empty string.');
+    throw new Error('The "server" option cannot be an empty string.');
   }
 
   let prerenderOptions;
@@ -270,6 +270,12 @@ export async function normalizeOptions(
     };
   }
 
+  if ((appShellOptions || ssrOptions || prerenderOptions) && !serverEntryPoint) {
+    throw new Error(
+      'The "server" option is required when enabling "ssr", "prerender" or "app-shell".',
+    );
+  }
+
   // Initial options to keep
   const {
     allowedCommonJsDependencies,

packages/angular_devkit/build_angular/src/tools/esbuild/application-code-bundle.ts

@@ -154,15 +154,8 @@ export function createServerCodeBundleOptions(
   target: string[],
   sourceFileCache: SourceFileCache,
 ): BuildOptions {
-  const {
-    jit,
-    serverEntryPoint,
-    workspaceRoot,
-    ssrOptions,
-    watch,
-    externalPackages,
-    prerenderOptions,
-  } = options;
+  const { serverEntryPoint, workspaceRoot, ssrOptions, watch, externalPackages, prerenderOptions } =
+    options;
 
   assert(
     serverEntryPoint,