Test double-loading libbinder.

This is in preparation for the technical possibility of vendor using
libbinder_ndk to communicate w/ Stable AIDL interfaces on system or for
other possible usecases which may use double loaded libbinder.

Bug: 136027762
Bug: 138450837
Test: atest binderVendorDoubleLoadTest
Change-Id: I7b166ae08954283b378e1f18d2c44dcf70e698c5
diff --git a/libs/binder/TEST_MAPPING b/libs/binder/TEST_MAPPING
index 136bdb0..8ae7e7a 100644
--- a/libs/binder/TEST_MAPPING
+++ b/libs/binder/TEST_MAPPING
@@ -4,6 +4,9 @@
       "name": "binderSafeInterfaceTest"
     },
     {
+      "name": "binderVendorDoubleLoadTest"
+    },
+    {
       "name": "binderDriverInterfaceTest"
     },
     {