bpo-30871: Add "make pythoninfo" (#3120)

Makefile.pre.in

@@ -999,6 +999,8 @@ TESTPYTHON=	$(RUNSHARED) ./$(BUILDPYTHON) $(TESTPYTHONOPTS)
 TESTRUNNER=	$(TESTPYTHON) $(srcdir)/Tools/scripts/run_tests.py
 TESTTIMEOUT=	1200
 
+.PHONY: test testall testuniversal buildbottest pythoninfo
+
 # Run a basic set of regression tests.
 # This excludes some tests that are particularly resource-intensive.
 test:		@DEF_MAKE_RULE@ platform
@@ -1037,6 +1039,9 @@ buildbottest:	build_all platform
 		fi
 		$(TESTRUNNER) -j 1 -u all -W --slowest --fail-env-changed --timeout=$(TESTTIMEOUT) $(TESTOPTS)
 
+pythoninfo: build_all
+		$(RUNSHARED) ./$(BUILDPYTHON) -m test.pythoninfo
+
 QUICKTESTOPTS=	$(TESTOPTS) -x test_subprocess test_io test_lib2to3 \
 		test_multibytecodec test_urllib2_localnet test_itertools \
 		test_multiprocessing_fork test_multiprocessing_spawn \