Adds cross-compiling support for arm/raspi

core/README.md

@@ -29,6 +29,42 @@ cargo build -p kordophone
 cargo build -p kordophoned --release
 ```
 
+## Raspberry Pi Zero (cross build)
+
+Recommended approach is `cross` (https://github.com/cross-rs/cross), which uses a containerized toolchain.
+
+Prereqs:
+
+- Install Docker or Podman
+- Install `cross`: `cargo install cross`
+
+Build ARMv6 (Pi Zero / Zero W):
+
+```bash
+cd core
+make pi-zero
+```
+
+Build aarch64 (Pi OS 64-bit / Pi 3+):
+
+```bash
+cd core
+make pi-aarch64
+```
+
+Notes:
+
+- The aarch64 cross build uses a Debian 11 (bullseye) container base image to keep glibc compatible with bullseye.
+
+Artifacts:
+
+- `target/cross/arm-unknown-linux-gnueabihf/arm-unknown-linux-gnueabihf/release/kordophoned`
+- `target/cross/arm-unknown-linux-gnueabihf/arm-unknown-linux-gnueabihf/release/kpcli`
+- `target/cross/arm-unknown-linux-gnueabihf/arm-unknown-linux-gnueabihf/release/kptui`
+- `target/cross/aarch64-unknown-linux-gnu/aarch64-unknown-linux-gnu/release/kordophoned`
+- `target/cross/aarch64-unknown-linux-gnu/aarch64-unknown-linux-gnu/release/kpcli`
+- `target/cross/aarch64-unknown-linux-gnu/aarch64-unknown-linux-gnu/release/kptui`
+
 ## `kordophoned` (Client Daemon)
 
 The daemon maintains a local cache, handles update cycles, and exposes IPC for GUI apps.