Cross-compiling from aarch64 to x86_64, error: unknown target 'x86_64'

[deze333]

Using M4 macOS as a host. Followed the instructions and successfully built two Linux SDKs:

> swift sdk list
6.0.2-RELEASE_ubuntu_jammy_aarch64
6.0.2-RELEASE_ubuntu_jammy_x86_64

Next created an example project cross-compilation-test, just as described in the docs.

Compiling on Apple Silicon for Linux with same architecture works:

swift build --swift-sdk 6.0.2-RELEASE_ubuntu_jammy_aarch64

Compiling on Apple Silicon for Linux with Intel architecture fails:

swift build --swift-sdk 6.0.2-RELEASE_ubuntu_jammy_x86_64

Building for debugging...
error: unknown target 'x86_64'