always build in prod mode

src/cli/index.ts

@@ -1,6 +1,8 @@
 import { build, export as exporter } from 'sapper/core.js';
 import { dest, dev, entry, src } from '../config';
 
+process.env.NODE_ENV = 'production';
+
 const cmd = process.argv[2];
 const start = Date.now();
 
@@ -14,9 +16,7 @@ if (cmd === 'build') {
 			console.error(err ? err.details || err.stack || err.message || err : 'Unknown error');
 		});
 } else if (cmd === 'export') {
-	const start = Date.now();
-
-	build({ dest, dev, entry, src })
+	build({ dest, dev: false, entry, src })
 		.then(() => exporter({ src, dest }))
 		.then(() => {
 			const elapsed = Date.now() - start;