Missed part of a patch from Stephen Wilson.

llvm-svn: 125220
diff --git a/lldb/source/Host/common/File.cpp b/lldb/source/Host/common/File.cpp
index e4b7f05..0901127 100644
--- a/lldb/source/Host/common/File.cpp
+++ b/lldb/source/Host/common/File.cpp
@@ -11,6 +11,7 @@
 #include "lldb/Host/File.h"
 
 #include <fcntl.h>
+#include <stdarg.h>
 
 #include "lldb/Core/Error.h"
 #include "lldb/Host/Config.h"