Add vendor_available: true to Android.bp.

Bug: 78570710
Test: Still builds.
Change-Id: I0e6ea3b0680ca80f62dde3f9f25366ef9b40fec8
diff --git a/Android.bp b/Android.bp
index 7ac864f..10471bc 100644
--- a/Android.bp
+++ b/Android.bp
@@ -60,5 +60,6 @@
     ],
     local_include_dirs: ["xkbcommon/src"],
     export_include_dirs: ["xkbcommon"],
+    vendor_available: true,
     name: "libxkbcommon",
 }