add cross-compilation build script using cargo-zigbuild

produces fully static, zero-dependency binaries for macOS (arm64)
and Linux (x86_64 musl). no Docker required — uses zig as the
cross-linker.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.gitignore

@@ -1,2 +1,3 @@
 /target/
+/dist/
 .DS_Store

build.sh

@@ -0,0 +1,47 @@
+#!/usr/bin/env bash
+# build.sh — build static uc binaries for all targets
+#
+# Produces fully static, zero-dependency binaries:
+#   dist/uc-aarch64-apple-darwin      (macOS Apple Silicon)
+#   dist/uc-x86_64-unknown-linux-musl (Linux x86_64, static)
+#
+# Requirements:
+#   - mise (manages rust toolchain)
+#   - zig + cargo-zigbuild (for Linux cross-compilation)
+#   - rustup target x86_64-unknown-linux-musl (one-time setup)
+#
+# Usage:
+#   ./build.sh              build all targets
+#   ./build.sh macos        build macOS only
+#   ./build.sh linux        build Linux only
+set -euo pipefail
+
+eval "$(mise activate bash 2>/dev/null)" || true
+
+DIST="dist"
+mkdir -p "$DIST"
+
+build_macos() {
+	echo "==> building macOS (aarch64-apple-darwin) ..."
+	cargo build --release
+	cp target/release/uc "$DIST/uc-aarch64-apple-darwin"
+	echo "[ok] $DIST/uc-aarch64-apple-darwin"
+}
+
+build_linux() {
+	echo "==> building Linux (x86_64-unknown-linux-musl) ..."
+	cargo zigbuild --release --target x86_64-unknown-linux-musl
+	cp target/x86_64-unknown-linux-musl/release/uc "$DIST/uc-x86_64-unknown-linux-musl"
+	echo "[ok] $DIST/uc-x86_64-unknown-linux-musl"
+}
+
+case "${1:-all}" in
+	macos) build_macos ;;
+	linux) build_linux ;;
+	all)   build_macos; build_linux ;;
+	*)     echo "usage: $0 [macos|linux|all]"; exit 1 ;;
+esac
+
+echo ""
+echo "==> done"
+ls -lh "$DIST"/uc-*