Un-blacklist the example/facebook directory

Summary:
We missed syncing a couple of commits to this directory. I'm trying to
clean up the mess now, this will allow commits to go through in the future.

Reviewed By: codemiller

Differential Revision: D8588446

fbshipit-source-id: e5355eccdc802aa45d01d31d3a87a86c32de2ec1

fb-examples/config/facebook/Haxl.php-example

@@ -21,6 +21,14 @@ use \Facebook\ShipIt\ {
 final class FacebookHaxl extends FBShipItConfig {
   const string ROOT = 'fbcode/haxl/core/';
 
+  <<__Override>>
+  protected static function getStripCommonFilesExceptions(): ImmVector<string> {
+    return ImmVector {
+      // example/facebook is public, but would be stripped by default
+      '@^'.self::ROOT.'example/facebook/@',
+    };
+  }
+
   <<__Override>>
   protected static function getDefaultStrippedFiles(): ImmVector<string> {
     return ImmVector {