Add missing FFI_GNUW64 enum
diff --git a/src/x86/ffitarget.h b/src/x86/ffitarget.h
index 3a0efa5..85ccedf 100644
--- a/src/x86/ffitarget.h
+++ b/src/x86/ffitarget.h
@@ -94,6 +94,7 @@ typedef enum ffi_abi {
FFI_UNIX64,
FFI_WIN64,
FFI_EFI64 = FFI_WIN64,
+ FFI_GNUW64,
FFI_LAST_ABI,
FFI_DEFAULT_ABI = FFI_UNIX64