libinstall target now contains:

	-PYTHONPATH=$(DESTDIR)$(LIBDEST) $(RUNSHARED) \
		$(PYTHON_FOR_BUILD) -Wi -c "import lib2to3.pygram, lib2to3.patcomp;lib2to3.patcomp.PatternCompiler()"
	...
	@for d in $(LIBSUBDIRS); \
	do \
		a=$(srcdir)/Lib/$$d; \
		if test ! -d $$a; then continue; else true; fi; \
		if test `ls $$a | wc -l` -lt 1; then continue; fi; \
		b=$(LIBDEST)/$$d; \
		for i in $$a/*; \

There is a small chance that with high parallelization the wildcard expansion in the last line will occur for $$a == lib2to3 before creation of pickles has finished, resulting in not installation of pickles.
The solution would be to move creation of pickles to a separate target and make it a dependency of libinstall target.