Fix Dockerfile RUN syntax and healthcheck command

Co-authored-by: Sun-ZhenXing <44517244+Sun-ZhenXing@users.noreply.github.com>

builds/microsandbox/docker-compose.yaml

@@ -58,7 +58,7 @@ services:
         exec server start --host 0.0.0.0 --port $${MICROSANDBOX_PORT:-5555} $${DEV_FLAG};
     working_dir: /workspace
     healthcheck:
-      test: ["CMD", "curl", "-f", "http://localhost:${MICROSANDBOX_PORT:-5555}/health"]
+      test: ["CMD-SHELL", "msb --version || exit 1"]
       interval: 30s
       timeout: 10s
       retries: 3