Fix the metadata include.

Change-Id: I6f495b58ccbba985049168d1cc6385e4d0f73bab
diff --git a/src/compiler_llvm/gbc_expander.cc b/src/compiler_llvm/gbc_expander.cc
index a0693a8..6e8ce12 100644
--- a/src/compiler_llvm/gbc_expander.cc
+++ b/src/compiler_llvm/gbc_expander.cc
@@ -26,6 +26,7 @@
 
 #include <llvm/ADT/STLExtras.h>
 #include <llvm/Intrinsics.h>
+#include <llvm/Metadata.h>
 #include <llvm/Pass.h>
 #include <llvm/Support/CFG.h>
 #include <llvm/Support/InstIterator.h>