Add retry logic for torchvision git clone (handles GitHub 503 errors)

PyTorch 2.8.0 compiled successfully in ~4 hours!
Adding retry for torchvision to handle transient GitHub API issues.

Author: alexnorell

docker/dockerfiles/Dockerfile.onnx.jetson.6.2.0

@@ -90,9 +90,11 @@ RUN git clone --recursive --branch v${PYTORCH_VERSION} https://github.com/pytorc
     python3 setup.py bdist_wheel && \
     python3 -m pip install dist/torch-*.whl
 
-# Compile torchvision from source
+# Compile torchvision from source (with retry for transient GitHub issues)
 WORKDIR /build/torchvision
-RUN git clone --branch v${TORCHVISION_VERSION} https://github.com/pytorch/vision && \
+RUN for i in 1 2 3; do \
+        git clone --branch v${TORCHVISION_VERSION} https://github.com/pytorch/vision && break || sleep 60; \
+    done && \
     cd vision && \
     export BUILD_VERSION=${TORCHVISION_VERSION} TORCH_CUDA_ARCH_LIST="8.7" && \
     export FORCE_CUDA=1 MAX_JOBS=${MAX_JOBS} && \