Add Docker-based Linux release build for Ubuntu 20.04 compatibility

build.sh

@@ -41,6 +41,16 @@ if [[ "${1:-}" == "--win-release" ]]; then
     exit $?
 fi
 
+# Check for --linux-release flag (builds inside Ubuntu 20.04 container for max compatibility)
+if [[ "${1:-}" == "--linux-release" ]]; then
+    shift
+    echo "Building Linux release inside Ubuntu 20.04 Docker container..."
+    sudo docker build -t hush-builder -f Dockerfile.build .
+    sudo docker run --rm -v "$SCRIPT_DIR:/hush3" hush-builder "$@"
+    echo "Docker build complete. Release is in release-linux/"
+    exit $?
+fi
+
 # run correct build script for detected OS
 if [[ "$OSTYPE" == "linux-gnu"* ]]; then
     check_and_clean_target "linux"