python3: Fix race condition when doing parallel builds

When doing parallel builds, host Python can install the python3 symlink
before the Python standard library is installed completely.

When this occurs, it is possible for other packages to detect the
python3 symlink and try to use host Python before it is fully installed.

This adds a patch to make commoninstall (where the standard library is
installed) a prerequisite of bininstall (where the python3 symlink is
installed), so that commoninstall is fully completed before bininstall
begins.

Patch has been submitted upstream:
python/cpython#104693

Fixes: openwrt#19241

Signed-off-by: Jeffery To <[email protected]>

Author: jefferyto

lang/python/python3/patches/027-install-python3-symlink-after-stdlib.patch

@@ -0,0 +1,11 @@
+--- a/Makefile.pre.in
++++ b/Makefile.pre.in
+@@ -1361,7 +1361,7 @@ altbininstall: $(BUILDPYTHON) @FRAMEWORK
+ 			$(DESTDIR)$(BINDIR)/python$(VERSION)$(EXE); \
+ 	fi
+ 
+-bininstall: altbininstall
++bininstall: commoninstall altbininstall
+ 	if test ! -d $(DESTDIR)$(LIBPC); then \
+ 		echo "Creating directory $(LIBPC)"; \
+ 		$(INSTALL) -d -m $(DIRMODE) $(DESTDIR)$(LIBPC); \