gh-103053: Fix make check-clean-src: check "python" program (#110449)

"make check-clean-src" now also checks if the "python" program is
found in the source directory: fail with an error if it does exist.

Author: vstinner

Makefile.pre.in

@@ -624,7 +624,8 @@ build_wasm: check-clean-src $(BUILDPYTHON) platform sharedmods \
 .PHONY: check-clean-src
 check-clean-src:
 	@if test -n "$(VPATH)" -a \( \
-	    -f "$(srcdir)/Programs/python.o" \
+	    -f "$(srcdir)/$(BUILDPYTHON)" \
+	    -o -f "$(srcdir)/Programs/python.o" \
 	    -o -f "$(srcdir)\Python/frozen_modules/importlib._bootstrap.h" \
 	\); then \
 		echo "Error: The source directory ($(srcdir)) is not clean" ; \

Misc/NEWS.d/next/Build/2023-10-06-02-15-23.gh-issue-103053.--7JUF.rst

@@ -0,0 +1,3 @@
+"make check-clean-src" now also checks if the "python" program is found in
+the source directory: fail with an error if it does exist. Patch by Victor
+Stinner.