fix(esbuild): inject esbuild helpers correctly for esbuild 0.25.9+ (#20940)

Author: sapphi-red

packages/vite/src/node/plugins/esbuild.ts

@@ -29,7 +29,7 @@ const debug = createDebugger('vite:esbuild')
 // IIFE content looks like `var MyLib = function() {`.
 // Spaces are removed and parameters are mangled when minified
 const IIFE_BEGIN_RE =
-  /(?:const|var)\s+\S+\s*=\s*function\([^()]*\)\s*\{\s*"use strict";/
+  /(?:const|var)\s+\S+\s*=\s*\(?function\([^()]*\)\s*\{\s*"use strict";/
 
 const validExtensionRE = /\.\w+$/
 const jsxExtensionsRE = /\.(?:j|t)sx\b/