Disable RCF in the JVM during CLJS build (in :require-macros scenario)

When the CLJ REPL and Shadow are sharing JVM, RCF tests are enabled at the CLJ repl and Shadow needs to disable JVM RCF tests during incremental builds because :require-macros in a CLJS file will cause the CLJ files to load, running tests if enabled.

https://shadow-cljs.github.io/docs/UsersGuide.html#compile-stages

(defn rcf-shadow-hook 
  {:shadow.build/stage #{:configure :flush}}
  [build-state & args]
  (case (:shadow.build/stage build-state)
    :configure (enable! false)
    :flush (enable!))
  build-state)

Start with the Shadow compile stages documentation linked in the issue and the rcf-shadow-hook example. Trace how :require-macros loads CLJ files during incremental builds, then identify the integration point for the :configure and :flush stages. Done means JVM RCF tests are disabled during Shadow builds and restored afterward without affecting the CLJ REPL.