Describe the bug

Local laplacian example when using JIT (compile_to_callable) shows black image when target is "host-cuda" (but works fine for "host"). Using prerelease pip wheel for Halide.

To Reproduce

Install Halide python from prerelease pip:

pip install -i https://test.pypi.org/simple/ halide

Put attached local_laplacian_app.py in Halide/python_bindings/apps --target "host"
local_laplacian_app.py.txt

Run python local_laplacian_app.py <some_image.jpg> output.png

Run ``python local_laplacian_app.py <some_image.jpg> output.png --target "host-cuda" `