A minimal zsh script that can be used by an Xcode External Build System target to build for iOS

build-rust-ios-lib.sh

#!/bin/zsh

# Clears environment variables set by Xcode by taking a whitelist approach.
# We only need our HOME and PATH, as well as the ACTION and CONFIGURATION set by Xcode
env -i HOME="$HOME" PATH="$PATH" ACTION="$ACTION" CONFIGURATION="$CONFIGURATION" \
  /bin/zsh -l -c "$(cat <<-'END_OF_SCRIPT'
    # Function to perform a clean build
    clean_build() {
      echo "Cleaning..."
      cargo clean
    }

    # Function to perform a debug build
    debug_build() {
      echo "Building Debug..."
      cargo build --lib --target x86_64-apple-ios
      cargo build --lib --target aarch64-apple-ios
      cargo build --lib --target aarch64-apple-ios-sim
    }

    # Function to perform a release build
    release_build() {
      echo "Building Release..."
      cargo build --lib --release --target x86_64-apple-ios
      cargo build --lib --release --target aarch64-apple-ios
      cargo build --lib --release --target aarch64-apple-ios-sim
    }

    # Execute multiple actions based on Xcode build arguments
    if [ "$ACTION" = "clean" ]; then
      clean_build
    elif [ "$CONFIGURATION" = "Debug" ]; then
      debug_build
    elif [ "$CONFIGURATION" = "Release" ]; then
      release_build
    else
      echo "Unknown build action ($ACTION) or configuration ($CONFIGURATION)"
      exit 1
    fi
END_OF_SCRIPT
)"

See https://fosstodon.org/@ianthetechie/110253317456547643 for a thread on what I'm trying to accomplish and why I wrote this script.