if I build my iPhone12 mini as a target, the error below will occur.
The Swift standard library from the toolchain cannot be used on devices.
Select a macOS or simulator run destination instead, or use a diffrent toolchain that only provides the compiler.
Objective C builds well.
The build method is as follows.
brew install cmake ninja git clone https://github.com/apple/swift.git swift cd swift utils/update-checkout --tag swift-5.9-RELEASE --clone utils/build-toolchain MyToolchain
Please let me know if anything is missing.