fix(@angular-devkit/build-angular): prevent hanging initial build during exception with esbuild

When using the experimental esbuild-based browser application builder and an exception is thrown
during the initial build, the process may hang indefinitely due to the Sass worker pool not
shutting down fully. This does not happen for rebuilds after the initial.  To remedy this
situation, The initial build is now wrapped in a try block to ensure that a full shutdown
of the Sass worker pool occurs.

Author: clydin

Diff for: packages/angular_devkit/build_angular/src/builders/browser-esbuild/index.ts

@@ -469,7 +469,7 @@ export async function* buildEsbuildBrowser(
       'JIT mode is currently not supported by this experimental builder. AOT mode must be used.',
     );
 
-    return { success: false };
+    return;
   }
 
   // Inform user of experimental status of builder and options
@@ -480,7 +480,7 @@ export async function* buildEsbuildBrowser(
   if (!projectName) {
     context.logger.error(`The 'browser-esbuild' builder requires a target to be specified.`);
 
-    return { success: false };
+    return;
   }
 
   const normalizedOptions = await normalizeOptions(context, projectName, initialOptions);
@@ -497,18 +497,24 @@ export async function* buildEsbuildBrowser(
     assertIsError(e);
     context.logger.error('Unable to create output directory: ' + e.message);
 
-    return { success: false };
+    return;
   }
 
   // Initial build
-  let result = await execute(normalizedOptions, context);
-  yield result.output;
-
-  // Finish if watch mode is not enabled
-  if (!initialOptions.watch) {
-    shutdownSassWorkerPool();
+  let result: ExecutionResult;
+  try {
+    result = await execute(normalizedOptions, context);
+    yield result.output;
 
-    return;
+    // Finish if watch mode is not enabled
+    if (!initialOptions.watch) {
+      return;
+    }
+  } finally {
+    // Ensure Sass workers are shutdown if not watching
+    if (!initialOptions.watch) {
+      shutdownSassWorkerPool();
+    }
   }
 
   context.logger.info('Watch mode enabled. Watching for file changes...');