don't delete .asf.yaml when generating new site
diff --git a/site-dev/build.gradle b/site-dev/build.gradle
index c0d406a..4797d00 100644
--- a/site-dev/build.gradle
+++ b/site-dev/build.gradle
@@ -157,7 +157,7 @@
 
         // Delete the previous content. These are asf-site branch paths.
         gitout.remove(patterns: ['.'])
-        fileTree(stagingDevSite).exclude('.git').visit { delete it.file }
+        fileTree(stagingDevSite).exclude('.git', '.asf.yaml').visit { delete it.file }
         assert !file("${stagingDevSite}/index.html").exists()
 
         // Copy the built content and add it.