add missing #includes


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@49020 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Archive/Archive.cpp b/lib/Archive/Archive.cpp
index 6c95dbe..125b22e 100644
--- a/lib/Archive/Archive.cpp
+++ b/lib/Archive/Archive.cpp
@@ -17,6 +17,7 @@
 #include "llvm/ModuleProvider.h"
 #include "llvm/Module.h"
 #include "llvm/Support/MemoryBuffer.h"
+#include "llvm/System/MappedFile.h"
 #include "llvm/System/Process.h"
 #include <memory>
 #include <cstring>