fix: use assetsDir in creating vite config

.changeset/afraid-laws-speak.md

@@ -0,0 +1,5 @@
+---
+"astro": minor
+---
+
+set build.assets directory during vite config setup

packages/astro/src/core/create-vite.ts

@@ -239,6 +239,14 @@ export async function createVite(
 	// We also need to filter out the plugins that are not meant to be applied to the current command:
 	// - If the command is `build`, we filter out the plugins that are meant to be applied for `serve`.
 	// - If the command is `dev`, we filter out the plugins that are meant to be applied for `build`.
+	const assetsDir = settings.config.build.assets;
+	if (assetsDir) {
+		result = vite.mergeConfig(result, {
+			build: {
+				assetsDir,
+			},
+		});
+	}
 	if (command && settings.config.vite?.plugins) {
 		let { plugins, ...rest } = settings.config.vite;
 		const applyToFilter = command === 'build' ? 'serve' : 'build';