build(aio): move file cleaning to later in the doc gen

aio/package.json

@@ -39,7 +39,6 @@
     "check-env": "yarn ~~check-env",
     "postcheck-env": "yarn aio-check-local",
     "payload-size": "scripts/payload.sh",
-    "predocs": "rimraf src/generated/{docs,*.json}",
     "docs": "dgeni ./tools/transforms/angular.io-package",
     "docs-watch": "node tools/transforms/authors-package/watchr.js",
     "docs-lint": "eslint --ignore-path=\"tools/transforms/.eslintignore\" tools/transforms",

aio/tools/transforms/angular.io-package/index.js

@@ -17,6 +17,7 @@ module.exports = new Package('angular.io', [gitPackage, apiPackage, contentPacka
 
   // This processor relies upon the versionInfo. See below...
   .processor(require('./processors/processNavigationMap'))
+  .processor(require('./processors/cleanGeneratedFiles'))
 
   // We don't include this in the angular-base package because the `versionInfo` stuff
   // accesses the file system and git, which is slow.

aio/tools/transforms/angular.io-package/processors/cleanGeneratedFiles.js

@@ -0,0 +1,10 @@
+const rimraf = require('rimraf');
+module.exports = function cleanGeneratedFiles() {
+  return {
+    $runAfter: ['writing-files'],
+    $runBefore: ['writeFilesProcessor'],
+    $process: function() {
+      rimraf.sync('src/generated/{docs,*.json}');
+    }
+  };
+};