ld: Invalid value (Producer: 'LLVM13.0.0-rust-1.57.0-nightly' Reader: 'LLVM APPLE_1_1300.0.29.3_0') for architecture arm64
The solution to this problem turns out to be deceptively simple: set the Xcode build setting "Enable Bitcode" to "No", as in this image:
(I figured this out by first discovering that command-line archive builds did not have this problem, and then comparing their log with the in-Xcode build log. The in-XCode build was doing bitcode-verify operations, which reminded me that the Rust cargo-lipo README talks about turning this setting off to avoid this LLVM incompatibility.)