php-wasm/build: Explicitly list the external dependencies

The esbuild.js config must export the config, not run the build.
This PR ensures that's the case and also that all the dependencies
are explicitly listed – unfortunately relying on the
esbuild-node-externals didn't solve the issue.

packages/php-wasm/node/esbuild.js

@@ -1,12 +1,10 @@
 const esbuild = require('esbuild');
-const { nodeExternalsPlugin } = require('esbuild-node-externals');
 
-esbuild.build({
+module.exports = {
 	entryPoints: [
 		'packages/php-wasm/node/src/index.ts',
 		'packages/php-wasm/node/src/noop.ts',
 	],
-	plugins: [nodeExternalsPlugin()],
 	supported: {
 		'dynamic-import': false,
 	},
@@ -21,10 +19,10 @@ esbuild.build({
 	},
 	bundle: true,
 	tsconfig: 'packages/php-wasm/node/tsconfig.json',
-	external: ['@php-wasm/*', '@wp-playground/*'],
+	external: ['@php-wasm/*', '@wp-playground/*', 'ws'],
 	loader: {
 		'.php': 'text',
 		'.ini': 'file',
 		'.wasm': 'file',
 	},
-});
+};