Whenever the sticker pack hits a certain number of animated stickers (or a certain file size), Xcode just gets stuck at "Compiling asset catalogs"...
This issue started since beta 4 (and contines to be a problem in beta 5 and beta 6) and I've filed 2 bug reports with no response so far.
It's beta 6 now and I'm extremely concerned I won't be able to submit it on day one after hours and hours of work.
There are multiple other developers having the same issue:
https://forums.developer.apple.com/thread/54234
https://forums.developer.apple.com/thread/54289
Multiple bug reports have been filed with no response:
27780400, 27651617, and 27789324
Please at the very least give us a status update...