fix: ngcc progress not reported

ngcc progress is supposed to be reported to the client, but since the child
process is not silenced, stdio got inherited from the parent process. As a
result, ngcc progress shows up in the Output panel of Angular language service
instead of the status bar in vscode.

Author: kyliau

server/src/ngcc.ts

@@ -47,6 +47,7 @@ export async function resolveAndRunNgcc(tsconfig: string, progress: Progress): P
       ],
       {
         cwd: resolve(cwd),
+        silent: true,  // pipe stderr and stdout so that we can report progress
       });
 
   let stderr = '';