UR opencl plugin compile error when using latest OpenCL-Headers

[sarnex]

Describe the bug

The problem is really stupid.

For some reason the OpenCL headers only define a struct member if ANSI strict mode is disabled or using clang, see here and here.

LLVM_ENABLE_PEDANTIC is on by default so ANSI strict mode is enabled (through -pedantic), so the struct member isn't defined so we get a compile error when trying to access it in the UR plugin.

So the build fails with gcc. I added a workaround in #19649.

To reproduce

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Environment

Additional context

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