I had a linking error on the missing destructor of WaitableEvent when updating to 5.4.7. I had to add it back manually since it was removed from 5.4.5. This is on Android.
The empty destructor was removed in c964a842 so now there will be a compiler-generated default destructor. We don’t declare a destructor anywhere so it’s odd that you would see a linker error. Can you paste the full output of the error? Is it possible that you haven’t updated all of your JUCE modules fully and there are multiple versions of JUCE being used?
You are right, apologies! A clean build fixed it.