[libc++] Don't define operator new/delete when using vcruntime

[thomasanderson]

Summary

Fixes build errors on Windows without libc++abi of the form:

new(173,36):  error: redeclaration of 'operator delete' cannot add 'dllexport' attribute
_LIBCPP_OVERRIDABLE_FUNC_VIS void  operator delete(void* __p) _NOEXCEPT;
vcruntime_new.h(87,16):  note: previous declaration is here
void __CRTDECL operator delete(
new(205,70):  error: redefinition of 'operator new'
_LIBCPP_NODISCARD_AFTER_CXX17 inline _LIBCPP_INLINE_VISIBILITY void* operator new  (std::size_t, void* __p) _NOEXCEPT {return __p;}
vcruntime_new.h(184,28):  note: previous definition is here
    inline void* __CRTDECL operator new(size_t _Size, _Writable_bytes_(_Size) void* _Where) noexcept
new(206,70):  error: redefinition of 'operator new[]'
_LIBCPP_NODISCARD_AFTER_CXX17 inline _LIBCPP_INLINE_VISIBILITY void* operator new[](std::size_t, void* __p) _NOEXCEPT {return __p;}
vcruntime_new.h(199,28):  note: previous definition is here
    inline void* __CRTDECL operator new[](size_t _Size,
new(207,40):  error: redefinition of 'operator delete'
inline _LIBCPP_INLINE_VISIBILITY void  operator delete  (void*, void*) _NOEXCEPT {}
vcruntime_new.h(190,27):  note: previous definition is here
    inline void __CRTDECL operator delete(void*, void*) noexcept
new(208,40):  error: redefinition of 'operator delete[]'
inline _LIBCPP_INLINE_VISIBILITY void  operator delete[](void*, void*) _NOEXCEPT {}
vcruntime_new.h(206,27):  note: previous definition is here
    inline void __CRTDECL operator delete[](void*, void*) noexcept

[thomasanderson]

Not sure if this is the right fix, but the issue goes away with this patch

[lebedev.ri]

This differential skipped -commits list during review.

include/__config

 #    define _LIBCPP_HAS_CATOPEN 1
 #  endif
 #endif
 
 #ifdef __FreeBSD__
 #define _DECLARE_C99_LDBL_MATH 1
 #endif
 
+#if defined(_LIBCPP_ABI_MICROSOFT) && !defined(_LIBCPP_NO_VCRUNTIME)
+#  define _LIBCPP_DEFER_NEW_TO_VCRUNTIME
+#endif
+
 // If we are getting operator new from the MSVC CRT, then allocation overloads
 // for align_val_t were added in 19.12, aka VS 2017 version 15.3.
 #if defined(_LIBCPP_MSVCRT) && defined(_MSC_VER) && _MSC_VER < 1912
 #  define _LIBCPP_HAS_NO_LIBRARY_ALIGNED_ALLOCATION
-#elif defined(_LIBCPP_ABI_MICROSOFT) && !defined(_LIBCPP_NO_VCRUNTIME)
-#  define _LIBCPP_DEFER_NEW_TO_VCRUNTIME
-#  if !defined(__cpp_aligned_new)
-     // We're defering to Microsoft's STL to provide aligned new et al. We don't
-     // have it unless the language feature test macro is defined.
-#    define _LIBCPP_HAS_NO_LIBRARY_ALIGNED_ALLOCATION
-#  endif
-#endif
+#elif defined(_LIBCPP_DEFER_NEW_TO_VCRUNTIME) && !defined(__cpp_aligned_new)
+#  define _LIBCPP_HAS_NO_LIBRARY_ALIGNED_ALLOCATION
+#endif
 
 #if defined(__APPLE__)
 #  if !defined(__MAC_OS_X_VERSION_MIN_REQUIRED) && \
       defined(__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__)
 #    define __MAC_OS_X_VERSION_MIN_REQUIRED __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__
 #  endif
 #endif // defined(__APPLE__)