[tests] Add support for running external test suites. (#2324)

mk/xamarin.mk

@@ -1,5 +1,5 @@
 ifdef ENABLE_XAMARIN
-NEEDED_MACCORE_VERSION := 7cc095bfd20d77e43a4ceed3c0e91ff546b743a9
+NEEDED_MACCORE_VERSION := 83265cab5e9346c2eb260e7f485a5c47a61e30b4
 NEEDED_MACCORE_BRANCH := master
 
 MACCORE_DIRECTORY := maccore

tests/Makefile

@@ -355,3 +355,11 @@ endif
 
 jenkins: xharness/xharness.exe
 	$(Q) $(SYSTEM_MONO) --debug $< $(XHARNESS_VERBOSITY) --jenkins --autoconf --rootdir $(CURDIR) --sdkroot $(XCODE_DEVELOPER_ROOT)
+
+ifdef ENABLE_XAMARIN
+wrench-launch-external wrench-report-external:
+	$(MAKE) -C $(MACCORE_PATH)/tests/external $@
+else
+wrench-launch-external wrench-report-external:
+	@echo "External tests have been disabled"
+endif