Add some build tooling

build_arm64.sh

@@ -0,0 +1,5 @@
+#!/bin/bash
+# requires cargo cross (cargo install cross)
+cross build --release --all --target aarch64-unknown-linux-musl
+
+./utils/package_release.py ./target/aarch64-unknown-linux-musl/release/ --output openjam_servers_linux_arm64.zip