root.bp: Add vendor/*/*

Vendors must be able to use Android.bp files without changing root.bp.

Bug: 33672964
Test: compiles
Change-Id: I3b1d0d530d700c96ab1404b31166f10e834a1952
diff --git a/root.bp b/root.bp
index 7e4636f..332032c 100644
--- a/root.bp
+++ b/root.bp
@@ -38,4 +38,5 @@
     "system/security/*",
     "system/tools/*",
     "test/vts",
+    "vendor/*/*",
 ]