fix(vant-cli): pnpm compatibility (#10214)

* fix(vant-cli): pnpm compatibility

* chore: clean code, semantic naming

packages/vant-cli/src/compiler/gen-package-style.ts

@@ -6,11 +6,11 @@ import { CSS_LANG, getCssBaseFile } from '../common/css.js';
 import { SRC_DIR, STYLE_DEPS_JSON_FILE } from '../common/constant.js';
 
 type Options = {
-  outputPath: string;
+  outputPath?: string;
   pathResolver?: (path: string) => string;
 };
 
-export function genPackageStyle(options: Options) {
+export function genPackageStyle(options: Options = {}) {
   const require = createRequire(import.meta.url);
   const styleDepsJson = require(STYLE_DEPS_JSON_FILE);
   const ext = '.' + CSS_LANG;
@@ -43,5 +43,9 @@ export function genPackageStyle(options: Options) {
     .filter((item: string) => !!item)
     .join('\n');
 
-  smartOutputFile(options.outputPath, content);
+  if (options.outputPath) {
+    smartOutputFile(options.outputPath, content);
+  } else {
+    return content;
+  }
 }