If you run script/test-self-host, you will get an error rooted in "No such namespace: goog.json.HybridJsonProcessor".
This is an easy fix, related to churn in Google Closure (the same was revised in ClojureScript here https://github.com/clojure/clojurescript/commit/92433701acc6f86665b81349dc8c9eb4048ec464#diff-f3636bf6a57757156bc27de61a49fe31L91)
Fixing that, you will see there are other things to address for self-hosting for the defmethod for cljs.test/assert-expr 'clojure.test.check.clojure-test/check? in the (clojure.test.check.clojure-test.assertions and clojure.test.check.clojure-test.assertions.cljs namespaces).
If these can be fixed, we can get the self host tests to be runnable again. (They may not yet all pass, but they can then be executed.)