fix PR9015, a crash linking recursive metadata.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@124099 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/Linker/linkmdnode2.ll b/test/Linker/linkmdnode2.ll
index 54a5a57..a7d991a 100644
--- a/test/Linker/linkmdnode2.ll
+++ b/test/Linker/linkmdnode2.ll
@@ -10,3 +10,13 @@
   %x = call i8 @llvm.something(metadata !22)
   ret void
 }
+
+
+
+; PR9015
+define void @test() {
+  ret void, !abc !0
+}
+
+!0 = metadata !{metadata !0, i32 42 }
+