[3.14] gh-141808: Don't remove the JIT stencils when building with PGO (GH-141809) (GH-142657)

See: https://discuss.python.org/t/building-the-jit-with-pre-built-stencils/91838/12
(cherry picked from commit 8914148151)

Co-authored-by: Miro Hrončok <miro@hroncok.cz>
Co-authored-by: Mikhail Efimov <efimov.mikhail@gmail.com>

Makefile.pre.in

@@ -834,7 +834,7 @@ check-app-store-compliance:
 
 # Profile generation build must start from a clean tree.
 profile-clean-stamp:
-	$(MAKE) clean
+	$(MAKE) clean-profile
 	touch $@
 
 # Compile with profile generation enabled.
@@ -3222,7 +3222,6 @@ clean-retain-profile: pycremoval
 	-rm -rf Python/deepfreeze
 	-rm -f Python/frozen_modules/*.h
 	-rm -f Python/frozen_modules/MANIFEST
-	-rm -f jit_stencils.h
 	-find build -type f -a ! -name '*.gc??' -exec rm -f {} ';'
 	-rm -f Include/pydtrace_probes.h
 	-rm -f profile-gen-stamp
@@ -3241,13 +3240,21 @@ profile-removal:
 	rm -f profile-run-stamp
 	rm -f profile-bolt-stamp
 
-.PHONY: clean
-clean: clean-retain-profile clean-bolt
+.PHONY: clean-profile
+clean-profile: clean-retain-profile clean-bolt
 	@if test @DEF_MAKE_ALL_RULE@ = profile-opt -o @DEF_MAKE_ALL_RULE@ = bolt-opt; then \
 		rm -f profile-gen-stamp profile-clean-stamp; \
 		$(MAKE) profile-removal; \
 	fi
 
+# gh-141808: The JIT stencils are deliberately kept in clean-profile
+.PHONY: clean-jit-stencils
+clean-jit-stencils:
+	-rm -f jit_stencils*.h
+
+.PHONY: clean
+clean: clean-profile clean-jit-stencils
+
 .PHONY: clobber
 clobber: clean
 	-rm -f $(BUILDPYTHON) $(LIBRARY) $(LDLIBRARY) $(DLLLIBRARY) \

Misc/NEWS.d/next/Build/2025-11-20-23-15-39.gh-issue-141808.NEewZC.rst

@@ -0,0 +1,4 @@
+When running ``make clean-retain-profile``, keep the
+generated JIT stencils. That way, the stencils are not generated twice when
+Profile-guided optimization (PGO) is used. It also allows distributors to
+supply their own pre-built JIT stencils.