build: cleanup stale bundles

package.json

@@ -8,6 +8,7 @@
   },
   "scripts": {
     "build": "util/build.py",
+    "build:cleanup": "rm -rf bundles",
     "build:bundles": "webpack",
     "build:regexps": "node util/makexregexps.js > data/xregexps.json",
     "stats": "cloc --vcs=git --exclude-lang=Markdown,SVG",

util/build.py

@@ -32,6 +32,7 @@ PERM_IGNORED_FX = set(("downloads.shelf", "webRequest", "webRequestBlocking"))
 PERM_IGNORED_CHROME = set(("menus", "sessions", "theme"))
 
 SCRIPTS = [
+  "yarn build:cleanup",
   "yarn build:regexps",
   "yarn build:bundles",
 ]