refactor: use fs.mkdir instead of mkdirp

src/build.ts

@@ -8,7 +8,6 @@ import { defu } from "defu";
 import { createHooks } from "hookable";
 import prettyBytes from "pretty-bytes";
 import { globby } from "globby";
-import mkdirp from "mkdirp";
 import { dumpObject, rmdir, tryRequire, resolvePreset } from "./utils";
 import type { BuildContext, BuildConfig, BuildOptions } from "./types";
 import { validatePackage, validateDependencies } from "./validate";
@@ -170,7 +169,7 @@ export async function build(
   if (options.clean) {
     for (const dir of new Set(options.entries.map((e) => e.outDir).sort())) {
       await rmdir(dir!);
-      await mkdirp(dir!);
+      await fsp.mkdir(dir!, { recursive: true });
     }
   }