i think it works

code/boot/include/efistdarg.h

@@ -0,0 +1,33 @@
+#ifndef _EFISTDARG_H_
+#define _EFISTDARG_H_
+
+/*++
+
+Copyright (c) 1998  Intel Corporation
+
+Module Name:
+
+    devpath.h
+
+Abstract:
+
+    Defines for parsing the EFI Device Path structures
+
+
+
+Revision History
+
+--*/
+
+#if !defined(GNU_EFI_USE_EXTERNAL_STDARG) && !defined(_MSC_VER)
+typedef __builtin_va_list va_list;
+
+# define va_start(v,l)	__builtin_va_start(v,l)
+# define va_end(v)	__builtin_va_end(v)
+# define va_arg(v,l)	__builtin_va_arg(v,l)
+# define va_copy(d,s)	__builtin_va_copy(d,s)
+#else
+# include <stdarg.h>
+#endif
+
+#endif