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

third_party/libcxx/include/support/ibm/support.h

+// -*- C++ -*-
+//===----------------------- support/ibm/support.h ----------------------===//
+//
+//                     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.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_SUPPORT_IBM_SUPPORT_H
+#define _LIBCPP_SUPPORT_IBM_SUPPORT_H
+
+extern "builtin" int __popcnt4(unsigned int);
+extern "builtin" int __popcnt8(unsigned long long);
+extern "builtin" unsigned int __cnttz4(unsigned int);
+extern "builtin" unsigned int __cnttz8(unsigned long long);
+extern "builtin" unsigned int __cntlz4(unsigned long long);
+extern "builtin" unsigned int __cntlz8(unsigned long long);
+
+// Builtin functions for counting population
+#define __builtin_popcount(x) __popcnt4(x)
+#define __builtin_popcountll(x) __popcnt8(x)
+#if defined(__64BIT__)
+#define __builtin_popcountl(x) __builtin_popcountll(x)
+#else
+#define __builtin_popcountl(x) __builtin_popcount(x)
+#endif
+
+// Builtin functions for counting trailing zeros
+#define __builtin_ctz(x) __cnttz4(x)
+#define __builtin_ctzll(x) __cnttz8(x)
+#if defined(__64BIT__)
+#define __builtin_ctzl(x) __builtin_ctzll(x)
+#else
+#define __builtin_ctzl(x) __builtin_ctz(x)
+#endif
+
+// Builtin functions for counting leading zeros
+#define __builtin_clz(x) __cntlz4(x)
+#define __builtin_clzll(x) __cntlz8(x)
+#if defined(__64BIT__)
+#define __builtin_clzl(x) __builtin_clzll(x)
+#else
+#define __builtin_clzl(x) __builtin_clz(x)
+#endif
+
+#if defined(__64BIT__)
+#define __SIZE_WIDTH__ 64
+#else
+#define __SIZE_WIDTH__ 32
+#endif
+
+#endif // _LIBCPP_SUPPORT_IBM_SUPPORT_H