Add more missing C / C++ headers

third_party/libcxx/csetjmp

@@ -0,0 +1,48 @@
+// -*- C++ -*-
+// clang-format off
+//===--------------------------- csetjmp ----------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_CSETJMP
+#define _LIBCPP_CSETJMP
+
+/*
+    csetjmp synopsis
+
+Macros:
+
+    setjmp
+
+namespace std
+{
+
+Types:
+
+    jmp_buf
+
+void longjmp(jmp_buf env, int val);
+
+}  // std
+
+*/
+
+#include "third_party/libcxx/__config"
+#include "libc/runtime/runtime.h"
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+using ::jmp_buf;
+using ::longjmp;
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif  // _LIBCPP_CSETJMP