work around missing __debug header in Xcode CLT 6.3

uses the LLVM 3.6 debug header from:
http://reviews.llvm.org/diffusion/L/browse/libcxx/tags/RELEASE_360/final/include/__debug

Workaround for Homebrew/homebrew#38514.

Closes Homebrew/homebrew#38735.

Library/ENV/include/6.3/__debug

+// -*- C++ -*-
+//===--------------------------- __debug ----------------------------------===//
+//
+//                     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_DEBUG_H
+#define _LIBCPP_DEBUG_H
+
+#include <__config>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+#if _LIBCPP_DEBUG_LEVEL >= 1
+#   include <cstdlib>
+#   include <cstdio>
+#   include <cstddef>
+#   ifndef _LIBCPP_ASSERT
+#      define _LIBCPP_ASSERT(x, m) ((x) ? (void)0 : (_VSTD::printf("%s\n", m), _VSTD::abort()))
+#   endif
+#endif
+
+#ifndef _LIBCPP_ASSERT
+#   define _LIBCPP_ASSERT(x, m) ((void)0)
+#endif
+
+#if _LIBCPP_DEBUG_LEVEL >= 2
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+struct _LIBCPP_TYPE_VIS __c_node;
+
+struct _LIBCPP_TYPE_VIS __i_node
+{
+    void* __i_;
+    __i_node* __next_;
+    __c_node* __c_;
+
+#ifndef _LIBCPP_HAS_NO_DELETED_FUNCTIONS
+    __i_node(const __i_node&) = delete;
+    __i_node& operator=(const __i_node&) = delete;
+#else
+private:
+    __i_node(const __i_node&);
+    __i_node& operator=(const __i_node&);
+public:
+#endif
+    _LIBCPP_INLINE_VISIBILITY
+    __i_node(void* __i, __i_node* __next, __c_node* __c)
+        : __i_(__i), __next_(__next), __c_(__c) {}
+    ~__i_node();
+};
+
+struct _LIBCPP_TYPE_VIS __c_node
+{
+    void* __c_;
+    __c_node* __next_;
+    __i_node** beg_;
+    __i_node** end_;
+    __i_node** cap_;
+
+#ifndef _LIBCPP_HAS_NO_DELETED_FUNCTIONS
+    __c_node(const __c_node&) = delete;
+    __c_node& operator=(const __c_node&) = delete;
+#else
+private:
+    __c_node(const __c_node&);
+    __c_node& operator=(const __c_node&);
+public:
+#endif
+    _LIBCPP_INLINE_VISIBILITY
+    __c_node(void* __c, __c_node* __next)
+        : __c_(__c), __next_(__next), beg_(nullptr), end_(nullptr), cap_(nullptr) {}
+    virtual ~__c_node();
+
+    virtual bool __dereferenceable(const void*) const = 0;
+    virtual bool __decrementable(const void*) const = 0;
+    virtual bool __addable(const void*, ptrdiff_t) const = 0;
+    virtual bool __subscriptable(const void*, ptrdiff_t) const = 0;
+
+    void __add(__i_node* __i);
+    _LIBCPP_HIDDEN void __remove(__i_node* __i);
+};
+
+template <class _Cont>
+struct _C_node
+    : public __c_node
+{
+    _C_node(void* __c, __c_node* __n)
+        : __c_node(__c, __n) {}
+
+    virtual bool __dereferenceable(const void*) const;
+    virtual bool __decrementable(const void*) const;
+    virtual bool __addable(const void*, ptrdiff_t) const;
+    virtual bool __subscriptable(const void*, ptrdiff_t) const;
+};
+
+template <class _Cont>
+bool
+_C_node<_Cont>::__dereferenceable(const void* __i) const
+{
+    typedef typename _Cont::const_iterator iterator;
+    const iterator* __j = static_cast<const iterator*>(__i);
+    _Cont* _Cp = static_cast<_Cont*>(__c_);
+    return _Cp->__dereferenceable(__j);
+}
+
+template <class _Cont>
+bool
+_C_node<_Cont>::__decrementable(const void* __i) const
+{
+    typedef typename _Cont::const_iterator iterator;
+    const iterator* __j = static_cast<const iterator*>(__i);
+    _Cont* _Cp = static_cast<_Cont*>(__c_);
+    return _Cp->__decrementable(__j);
+}
+
+template <class _Cont>
+bool
+_C_node<_Cont>::__addable(const void* __i, ptrdiff_t __n) const
+{
+    typedef typename _Cont::const_iterator iterator;
+    const iterator* __j = static_cast<const iterator*>(__i);
+    _Cont* _Cp = static_cast<_Cont*>(__c_);
+    return _Cp->__addable(__j, __n);
+}
+
+template <class _Cont>
+bool
+_C_node<_Cont>::__subscriptable(const void* __i, ptrdiff_t __n) const
+{
+    typedef typename _Cont::const_iterator iterator;
+    const iterator* __j = static_cast<const iterator*>(__i);
+    _Cont* _Cp = static_cast<_Cont*>(__c_);
+    return _Cp->__subscriptable(__j, __n);
+}
+
+class _LIBCPP_TYPE_VIS __libcpp_db
+{
+    __c_node** __cbeg_;
+    __c_node** __cend_;
+    size_t   __csz_;
+    __i_node** __ibeg_;
+    __i_node** __iend_;
+    size_t   __isz_;
+
+    __libcpp_db();
+public:
+#ifndef _LIBCPP_HAS_NO_DELETED_FUNCTIONS
+    __libcpp_db(const __libcpp_db&) = delete;
+    __libcpp_db& operator=(const __libcpp_db&) = delete;
+#else
+private:
+    __libcpp_db(const __libcpp_db&);
+    __libcpp_db& operator=(const __libcpp_db&);
+public:
+#endif
+    ~__libcpp_db();
+
+    class __db_c_iterator;
+    class __db_c_const_iterator;
+    class __db_i_iterator;
+    class __db_i_const_iterator;
+
+    __db_c_const_iterator __c_end() const;
+    __db_i_const_iterator __i_end() const;
+
+    template <class _Cont>
+    _LIBCPP_INLINE_VISIBILITY
+    void __insert_c(_Cont* __c)
+    {
+        __c_node* __n = __insert_c(static_cast<void*>(__c));
+        ::new(__n) _C_node<_Cont>(__n->__c_, __n->__next_);
+    }
+
+    void __insert_i(void* __i);
+    __c_node* __insert_c(void* __c);
+    void __erase_c(void* __c);
+
+    void __insert_ic(void* __i, const void* __c);
+    void __iterator_copy(void* __i, const void* __i0);
+    void __erase_i(void* __i);
+
+    void* __find_c_from_i(void* __i) const;
+    void __invalidate_all(void* __c);
+    __c_node* __find_c_and_lock(void* __c) const;
+    __c_node* __find_c(void* __c) const;
+    void unlock() const;
+
+    void swap(void* __c1, void* __c2);
+
+
+    bool __dereferenceable(const void* __i) const;
+    bool __decrementable(const void* __i) const;
+    bool __addable(const void* __i, ptrdiff_t __n) const;
+    bool __subscriptable(const void* __i, ptrdiff_t __n) const;
+    bool __less_than_comparable(const void* __i, const void* __j) const;
+private:
+    _LIBCPP_HIDDEN
+    __i_node* __insert_iterator(void* __i);
+    _LIBCPP_HIDDEN
+    __i_node* __find_iterator(const void* __i) const;
+
+    friend _LIBCPP_FUNC_VIS __libcpp_db* __get_db();
+};
+
+_LIBCPP_FUNC_VIS __libcpp_db* __get_db();
+_LIBCPP_FUNC_VIS const __libcpp_db* __get_const_db();
+
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif
+
+#endif  // _LIBCPP_DEBUG_H
+

Library/Homebrew/extend/ENV/super.rb

@@ -161,7 +161,15 @@ module Superenv
   end
 
   def determine_include_paths
-    keg_only_deps.map { |dep| "#{HOMEBREW_PREFIX}/opt/#{dep}/include" }.to_path_s
+    paths = keg_only_deps.map { |dep| "#{HOMEBREW_PREFIX}/opt/#{dep}/include" }
+
+    # https://github.com/Homebrew/homebrew/issues/38514
+    if MacOS.clt_installed? && MacOS.active_developer_dir.include?("CommandLineTools") &&
+       MacOS::CLT.version == "6.3.0.0.1.1428348375"
+      paths << "#{HOMEBREW_LIBRARY}/ENV/include/6.3"
+    end
+
+    paths.to_path_s
   end
 
   def determine_library_paths