Add cross-compilation support for Linux and Windows

- Add Docker-based build system for cross-compiling on Apple Silicon
- Create Dockerfiles for Linux x86_64 and ARM64, Windows x86_64
- Add build-all.sh script for automated multi-platform builds
- Configure cargo-deb and cargo-generate-rpm for Linux packaging
- Update README with cross-compilation instructions

Supported outputs:
- Linux x86_64: .deb, .rpm, .tar.gz
- Windows x86_64: .zip

Note: Linux ARM64 disabled due to upstream zune-jpeg NEON bug

scripts/build-all.sh

@@ -0,0 +1,90 @@
+#!/bin/bash
+set -e
+
+# Cross-compilation build script for AVIF Maker
+# Uses Docker directly (not cross tool) for Apple Silicon compatibility
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+PROJECT_DIR="$(dirname "$SCRIPT_DIR")"
+cd "$PROJECT_DIR"
+
+VERSION=${1:-$(grep '^version' Cargo.toml | head -1 | sed 's/.*"\(.*\)".*/\1/')}
+DIST_DIR="dist/$VERSION"
+
+# Handle --setup-docker flag
+if [[ "$1" == "--setup-docker" ]]; then
+    echo "Building Docker images for cross-compilation..."
+    echo ""
+    echo "Building Linux x86_64 image..."
+    docker build --platform linux/amd64 -t avif-maker-linux-x86_64 -f docker/Dockerfile.linux-x86_64 .
+    echo ""
+    echo "Building Linux ARM64 image..."
+    docker build --platform linux/amd64 -t avif-maker-linux-arm64 -f docker/Dockerfile.linux-arm64 .
+    echo ""
+    echo "Building Windows x86_64 image..."
+    docker build --platform linux/amd64 -t avif-maker-windows-x86_64 -f docker/Dockerfile.windows-x86_64 .
+    echo ""
+    echo "Docker images built successfully!"
+    echo "You can now run: ./scripts/build-all.sh"
+    exit 0
+fi
+
+mkdir -p "$DIST_DIR"
+
+echo "Building AVIF Maker v$VERSION"
+echo "================================"
+
+# Check if Docker images exist
+if ! docker image inspect avif-maker-linux-x86_64 >/dev/null 2>&1; then
+    echo "Docker images not found. Run './scripts/build-all.sh --setup-docker' first."
+    exit 1
+fi
+
+# Linux x86_64
+echo ""
+echo "Building and packaging Linux x86_64..."
+docker run --rm --platform linux/amd64 \
+    -v "$PROJECT_DIR:/build" \
+    -w /build \
+    avif-maker-linux-x86_64 \
+    bash -c "
+        set -e
+        echo 'Compiling...'
+        cargo build --release --target x86_64-unknown-linux-gnu
+        echo 'Stripping binary...'
+        strip target/x86_64-unknown-linux-gnu/release/avif-maker
+        echo 'Creating .deb package...'
+        cargo deb --target x86_64-unknown-linux-gnu --no-build -o dist/$VERSION/
+        echo 'Creating .rpm package...'
+        cargo generate-rpm --target x86_64-unknown-linux-gnu -o dist/$VERSION/
+    "
+
+# Create tarball (can run on host)
+echo "Creating tarball..."
+tar -czvf "$DIST_DIR/avif-maker-$VERSION-linux-x86_64.tar.gz" \
+    -C target/x86_64-unknown-linux-gnu/release avif-maker
+
+# Linux ARM64  
+# NOTE: ARM64 cross-compilation is currently disabled due to upstream zune-jpeg NEON bug.
+# Build ARM64 natively on a Linux ARM64 system instead.
+echo ""
+echo "Skipping Linux ARM64 (upstream zune-jpeg bug with NEON cross-compilation)"
+echo "To build ARM64, run natively on a Linux ARM64 system."
+
+# Windows x86_64
+echo ""
+echo "Building Windows x86_64..."
+docker run --rm --platform linux/amd64 \
+    -v "$PROJECT_DIR:/build" \
+    -w /build \
+    avif-maker-windows-x86_64 \
+    cargo build --release --target x86_64-pc-windows-gnu
+
+zip -j "$DIST_DIR/avif-maker-$VERSION-windows-x86_64.zip" \
+    target/x86_64-pc-windows-gnu/release/avif-maker.exe
+
+echo ""
+echo "================================"
+echo "Build complete! Artifacts in $DIST_DIR/"
+echo ""
+ls -la "$DIST_DIR/"