[compiler-rt] [compiler-rt][test] Use configured Python for lit page-size probe (PR #209175)

[Simi Pallipurath via llvm-commits]

simpal01 wrote:

I agree that an explicit page-size setting for emulator runs would be the most complete solution, but I think it is more invasive than we need for this fix. And emulator configurations can vary by target architecture  so getting this right would require additional configuration plumbing.

 For the immediate issue, the old behaviour was already unreliable under emulators: if page-size detection failed, it fell back to 4096 and could silently advertise page-size-4096 for a target whose actual page size was unknown or different.

When i checked page-size-4096 , it only enables a small number of sanitizer tests (asan) that assume a 4 KiB page size.  I think for ATfE (Arm toolchain for Embedded)emulator configurations, the page-size-4096 feature has limited value.

That said,   It would be useful to hear if others have a preference or know of emulator configurations that rely on
this feature.

https://github.com/llvm/llvm-project/pull/209175