新裝的VS2015，調試舊的代碼報錯，信息如下：
MSB8020 The build tools for v120 (Platform Toolset = 'v120') cannot be found. To build using the v120 build tools, please install v120 build tools. Alternatively, you may upgrade to the current Visual Studio tools by selecting the Project menu or right-click
the solution, and then selecting "Retarget solution". Gtk-sfr-Demo C:\Program Files (x86)\MSBuild\Microsoft.Cpp\v4.0\V140\Microsoft.Cpp.Platform.targets 57
看到錯誤，首先想到可能是因爲之前的工程是用VS2013開發的，需要設置。 果斷百度之……
平臺工具集 改爲VS2015支持的即可： Visual Studio 2015 (v140)
