Missing Simulator Architectures for WatchOS 6 and later

[L6Echo]

For WatchOS 6 and later the Architecture x86_64 for Intel and arm64 for M1 is required. Currently only the Architecture i386, which was used for WatchOS 5 and earlier, is included in J2Objc watch lib.

[tomball]

This should have been fixed in 821ff4e. Since this pull request was merged after the last release, you'll need to build from source. "Real" developers should normally be doing that anyway, since the releases are really just for people who want to experiment with this project before seriously using it.

[tomball]

Please note: our team doesn't have any M1 hardware, since it's scarce and other Google iOS teams (with shipping apps) have higher priority. If architectural slices are missing from j2objc's build, we're therefore relying on pull requests from external developers to add that support, like 821ff4e was.

[L6Echo]

The mentioned commit adds "only" the arm64 for iPhone Simulator.

For watchOS Simulator only the architecture i386 can be build from source. i386 is only compatible for WatchOS 5 and earlier. When addressing watchOS 6 and later it is not possible right now to build for the Simulator (neither M1 nor Intel) neither with the release builds nor when compiling the source code.

I am not too deep into how the build scripts work, but I will try to add it and create a PR.