Revert "use rollup watch when in watch mode"

This reverts commit de386a6.

lib/index.js

@@ -67,20 +67,12 @@ function createPreprocessor(preconfig, config, emitter, logger) {
 				options.output.dir = path.dirname(originalPath)
 			}
 
-			let bundle;
-			options.cache = false;
+			let bundle = await rollup.rollup(options)
+			cache.set(originalPath, bundle.cache)
 
 			if (watcher) {
-				const watch = await rollup.watch(options);
-				bundle = await new Promise(res => watch.on('event', ( { result, code }) => {
-					if (code === 'BUNDLE_END') return res(result);
-				}));
-
 				let [entry, ...dependencies] = bundle.watchFiles
 				watcher.add(entry, dependencies)
-			} else {
-				bundle = await rollup.rollup(options)
-				cache.set(originalPath, bundle.cache)
 			}
 
 			log.info('Generating bundle for ./%s', location)