gh-142454: Make the JIT digest more deterministic by sorting the files in Tools/jit

Misc/NEWS.d/next/Build/2025-12-09-13-33-46.gh-issue-142454.cqUxzQ.rst

@@ -0,0 +1,4 @@
+When calculating the digest of the JIT stencils input, sort the hashed files
+by filenames before adding their content to the hasher. This ensures
+deterministic hash input and hence deterministic hash, independent on
+filesystem order.

Tools/jit/_targets.py

@@ -76,7 +76,7 @@ def _compute_digest(self) -> str:
             # Exclude cache files from digest computation to ensure reproducible builds.
             if dirpath.endswith("__pycache__"):
                 continue
-            for filename in filenames:
+            for filename in sorted(filenames):
                 hasher.update(pathlib.Path(dirpath, filename).read_bytes())
         return hasher.hexdigest()