Add safe_union@1.0::Monostate.

This is a helper type used to easily make optional types.

Bug: 116156870
Test: hidl_test, hidl_test_java
Change-Id: If38827800edf362676a99619c3d75114ab8eef13
diff --git a/update-makefiles.sh b/update-makefiles.sh
index 1a0b892..cf13c83 100755
--- a/update-makefiles.sh
+++ b/update-makefiles.sh
@@ -7,6 +7,7 @@
     android.hidl.manager@1.1
     android.hidl.manager@1.2
     android.hidl.memory@1.0
+    android.hidl.safe_union@1.0
     android.hidl.token@1.0
 )