Bump maccore to get a few mlaunch fixes. (#3628)

Commit list for xamarin/maccore:

* xamarin/maccore@689fae7440 Bump maciostools to get a few mlaunch fixes.

Diff: c76baed02b...689fae7440

mk/xamarin.mk

@@ -1,5 +1,5 @@
 ifdef ENABLE_XAMARIN
-NEEDED_MACCORE_VERSION := c76baed02bb6a3b70e6d71b2792bf05fbca42e57
+NEEDED_MACCORE_VERSION := 689fae744085835eba9ca9769630f2d5f8a17fff
 NEEDED_MACCORE_BRANCH := master
 
 MACCORE_DIRECTORY := maccore