pythongh-138061: Exclude __pycache__ directory from the computed digest in the JIT stencils (python#138131)

Exclude the __pycache__ directory when generating the digest in the JIT stencils

Author: alonme

Misc/NEWS.d/next/Build/2025-08-27-09-52-45.gh-issue-138061.fMVS9w.rst

@@ -0,0 +1 @@
+Ensure reproducible builds by making JIT stencil header generation deterministic.

Tools/jit/_targets.py

@@ -71,6 +71,9 @@ def _compute_digest(self) -> str:
         hasher.update(PYTHON_EXECUTOR_CASES_C_H.read_bytes())
         hasher.update((self.pyconfig_dir / "pyconfig.h").read_bytes())
         for dirpath, _, filenames in sorted(os.walk(TOOLS_JIT)):
+            # Exclude cache files from digest computation to ensure reproducible builds.
+            if dirpath.endswith("__pycache__"):
+                continue
             for filename in filenames:
                 hasher.update(pathlib.Path(dirpath, filename).read_bytes())
         return hasher.hexdigest()