[3.13] GH-118943: Handle races when moving jit_stencils.h (GH-122709)

(cherry picked from commit 44659d3)

Co-authored-by: Miro Hrončok <[email protected]>
Co-authored-by: Kirill Podoprigora <[email protected]>

Author: 3 people

Misc/NEWS.d/next/Build/2024-06-18-15-28-25.gh-issue-118943.aie7nn.rst

@@ -0,0 +1,3 @@
+Fix a possible race condition affecting parallel builds configured with
+``--enable-experimental-jit``, in which :exc:`FileNotFoundError` could be caused by
+another process already moving ``jit_stencils.h.new`` to ``jit_stencils.h``.

Tools/jit/_targets.py

@@ -221,7 +221,12 @@ def build(
                 file.write("\n")
                 for line in _writer.dump(stencil_groups):
                     file.write(f"{line}\n")
-            jit_stencils_new.replace(jit_stencils)
+            try:
+                jit_stencils_new.replace(jit_stencils)
+            except FileNotFoundError:
+                # another process probably already moved the file
+                if not jit_stencils.is_file():
+                    raise
         finally:
             jit_stencils_new.unlink(missing_ok=True)