But for a pure pre-compiled example there is Apple Bitcode which is meant to be compiled to the destination architecture before run (as opposed to JIT code which is compiled when run). It's mandatory for Apple watchOS apps and when they released watch with a 64bit CPU they just recompiled all the apps.
I believe that the binaries that actually get shipped to the watch are final bits. Apple just compiles the bitcode that developers give them into versions for all of the watches that they are supporting, and those versions get downloaded by the actual watches.
If they come out with new watches, then they can re-compile all of the code for the new watches with no developer involvement. It is really the best solution for all involved.
But for a pure pre-compiled example there is Apple Bitcode which is meant to be compiled to the destination architecture before run (as opposed to JIT code which is compiled when run). It's mandatory for Apple watchOS apps and when they released watch with a 64bit CPU they just recompiled all the apps.