Add libc++ and libc++abi to third-party.

third_party/libc++/src/random.cpp

+//===-------------------------- random.cpp --------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#if defined(_WIN32)
+// Must be defined before including stdlib.h to enable rand_s().
+#define _CRT_RAND_S
+#include <stdio.h>
+#endif
+
+#include "random"
+#include "system_error"
+
+#ifdef __sun__
+#define rename solaris_headers_are_broken
+#endif
+#include <fcntl.h>
+#include <unistd.h>
+#include <errno.h>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if defined(_WIN32)
+random_device::random_device(const string&)
+{
+}
+
+random_device::~random_device()
+{
+}
+
+unsigned
+random_device::operator()()
+{
+    unsigned r;
+    errno_t err = rand_s(&r);
+    if (err)
+        __throw_system_error(err, "random_device rand_s failed.");
+    return r;
+}
+#else
+random_device::random_device(const string& __token)
+    : __f_(open(__token.c_str(), O_RDONLY))
+{
+    if (__f_ <= 0)
+        __throw_system_error(errno, ("random_device failed to open " + __token).c_str());
+}
+
+random_device::~random_device()
+{
+    close(__f_);
+}
+
+unsigned
+random_device::operator()()
+{
+    unsigned r;
+    read(__f_, &r, sizeof(r));
+    return r;
+}
+#endif // defined(_WIN32)
+
+double
+random_device::entropy() const _NOEXCEPT
+{
+    return 0;
+}
+
+_LIBCPP_END_NAMESPACE_STD