build: build .langium file using generate from langium-cli

.build/generateLangium.ts

@@ -1,11 +1,5 @@
-import { execFileSync } from 'child_process';
+import { generate } from 'langium-cli';
 
-export function generateLangium() {
-  execFileSync('pnpm', [
-    '--prefix',
-    `${process.cwd()}/packages/parser`,
-    'exec',
-    'langium',
-    'generate',
-  ]);
+export async function generateLangium() {
+  await generate({ file: `./packages/parser/langium-config.json` });
 }