Add __libcpp_allocate and __libcpp_deallocate in the absense of align allocation and sized deallocation

Author: zibi2

libcxx/include/__utility/small_buffer.h

@@ -61,26 +61,30 @@ class __small_buffer {
       return *std::launder(reinterpret_cast<_Stored**>(__buffer_));
   }
 
-#  ifdef _LIBCPP_HAS_LIBRARY_ALIGNED_ALLOCATION
   template <class _Stored>
   _LIBCPP_HIDE_FROM_ABI _Stored* __alloc() {
     if constexpr (__fits_in_buffer<_Stored>) {
       return std::launder(reinterpret_cast<_Stored*>(__buffer_));
     } else {
+#  ifdef _LIBCPP_HAS_LIBRARY_ALIGNED_ALLOCATION
       byte* __allocation = static_cast<byte*>(::operator new[](sizeof(_Stored), align_val_t{alignof(_Stored)}));
       std::construct_at(reinterpret_cast<byte**>(__buffer_), __allocation);
       return std::launder(reinterpret_cast<_Stored*>(__allocation));
+#  else
+      return static_cast<_Stored*>(std::__libcpp_allocate(_BufferSize* sizeof(byte), _LIBCPP_ALIGNOF(byte)));
+#  endif // _LIBCPP_HAS_LIBRARY_ALIGNED_ALLOCATION
     }
   }
 
-#  endif // _LIBCPP_HAS_LIBRARY_ALIGNED_ALLOCATION
-#  ifdef _LIBCPP_HAS_LIBRARY_SIZED_DEALLOCATION
   template <class _Stored>
   _LIBCPP_HIDE_FROM_ABI void __dealloc() noexcept {
     if constexpr (!__fits_in_buffer<_Stored>)
+#  ifdef _LIBCPP_HAS_LIBRARY_SIZED_DEALLOCATION
       ::operator delete[](*reinterpret_cast<void**>(__buffer_), sizeof(_Stored), align_val_t{alignof(_Stored)});
-  }
+#  else
+      std::__libcpp_deallocate((void*)__buffer_, _BufferSize * sizeof(byte), _LIBCPP_ALIGNOF(_Stored));
 #  endif // _LIBCPP_HAS_LIBRARY_SIZED_DEALLOCATION
+  }
 
   template <class _Stored, class... _Args>
   _LIBCPP_HIDE_FROM_ABI void __construct(_Args&&... __args) {