warn about disappearing prerendered files

packages/astro/src/core/build/generate.ts

@@ -524,6 +524,8 @@ async function generatePath(
 	if (response.status >= 300 && response.status < 400) {
 		// If redirects is set to false, don't output the HTML
 		if (!config.build.redirects) {
+			throw new Error;
+			logger.warn("build", `In static builds, redirects must be performed using the \`build.redirects\` configuration. However, the "${pathname}" path returned a response with a ${response.status} HTTP code. As a result, a file for this path will not be built.`);
 			return;
 		}
 		const locationSite = getRedirectLocationOrThrow(response.headers);