fix(Build.py): add missing --userdataobj CLI flag

[simonCatBot]

Problem: The new GitHub Actions CI workflow introduced --userdataobj as a build flag for Build.py, but Build.py did not support it, causing the entire CI pipeline to fail with:

Build.py: error: no such option: --userdataobj

Fix: Add the missing --userdataobj CLI flag to Build.py, which sets -DOPENVX_USE_USER_DATA_OBJECT=ON for the CMake configure step.

CMakeLists.txt already defines and supports OPENVX_USE_USER_DATA_OBJECT, so this simply wires the CLI option through to CMake.

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