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

[via llvm-commits]

maflcko wrote:

CI log before: https://github.com/llvm/llvm-project/actions/runs/29232941997/job/86760988390#step:4:8854

```
  llvm-lit.py: C:\_work\llvm-project\llvm-project\llvm\utils\lit\lit\llvm\config.py:64: note: using lit tools: C:\Program Files\Git\usr\bin
  'python3' is not recognized as an internal or external command,
  operable program or batch file.
  'python3' is not recognized as an internal or external command,
  operable program or batch file.
  'python3' is not recognized as an internal or external command,
  operable program or batch file.
  'python3' is not recognized as an internal or external command,
  operable program or batch file.
  'python3' is not recognized as an internal or external command,
  operable program or batch file.
  'python3' is not recognized as an internal or external command,
  operable program or batch file.
  'python3' is not recognized as an internal or external command,
  operable program or batch file.
  'python3' is not recognized as an internal or external command,
  operable program or batch file.
  'python3' is not recognized as an internal or external command,
  operable program or batch file.
  'python3' is not recognized as an internal or external command,
  operable program or batch file.
  'python3' is not recognized as an internal or external command,
  operable program or batch file.
  'python3' is not recognized as an internal or external command,
  operable program or batch file.
  'python3' is not recognized as an internal or external command,
  operable program or batch file.
  -- Testing: 2564 tests, 32 workers --
  Testing:  0.. 10.. 20.. 30.. 40.. 50.. 60.. 70.. 80.. 90.. 
  Slowest Tests:
  --------------------------------------------------------------------------
...
  
  Testing Time: 106.43s
  
  Total Discovered Tests: 3016
    Unsupported      : 1360 (45.09%)
    Passed           : 1620 (53.71%)
    Expectedly Failed:   36 (1.19%)
```

After: https://github.com/llvm/llvm-project/actions/runs/29253629902/job/86827926908?pr=209175#step:4:6445:

```
  llvm-lit.py: C:\_work\llvm-project\llvm-project\llvm\utils\lit\lit\llvm\config.py:64: note: using lit tools: C:\Program Files\Git\usr\bin
  -- Testing: 2566 tests, 32 workers --
  Testing:  0.. 10.. 20.. 30.. 40.. 50.. 60.. 70.. 80.. 90..
  Slowest Tests:
  --------------------------------------------------------------------------
...
  
  Testing Time: 99.15s
  
  Total Discovered Tests: 3018
    Unsupported      : 1360 (45.06%)
    Passed           : 1622 (53.74%)
    Expectedly Failed:   36 (1.19%)


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