[llvm] [offload][cmake] always define pythonize_bool macro (PR #96028)

[Wu Yingcong via llvm-commits]

yingcong-wu wrote:

Yes, that would still have the same problem. The problem of **only** putting `offload` to `LLVM_ENABLE_RUNTIMES` is that it does not define its `pythonize_bool` in this case(if I put `openmp` to `LLVM_ENABLE_RUNTIMES`, then `offload` will use the `pythonize_bool` defined in `openmp` and will not have this problem), so I am trying to make it always define the `pythonize_bool`. 

https://github.com/llvm/llvm-project/pull/96028