Add a WinStore-x86_64 cmake toolchain

.appveyor.yml

@@ -12,6 +12,7 @@ environment:
     - toolchain: "Windows-x86_64"
     - toolchain: "Windows-x86"
     - toolchain: "WinStore-x86"
+    - toolchain: "WinStore-x86_64"
     - toolchain: "WinStore-ARM"
 
 clone_folder: c:\projects\ds2

Support/CMake/Toolchain-WinStore-x86_64.cmake

@@ -0,0 +1,18 @@
+##
+## Copyright (c) 2014-present, Facebook, Inc.
+## All rights reserved.
+##
+## This source code is licensed under the University of Illinois/NCSA Open
+## Source License found in the LICENSE file in the root directory of this
+## source tree. An additional grant of patent rights can be found in the
+## PATENTS file in the same directory.
+##
+
+set(CMAKE_SYSTEM_NAME WindowsStore)
+set(CMAKE_SYSTEM_VERSION 10.0)
+set(CMAKE_GENERATOR_PLATFORM x64)
+
+# For WinStore we build as a library because creating a process seems
+# restricted, so we just have a separate process open `ds2.dll` and run `main`
+# from it.
+set(LIBRARY 1)