Earlier versions of MSBuild could be found here: %programfiles(x86)%\\msbuild\\\\bin\\msbuild.exe.
%programfiles(x86)%\\msbuild\\\\bin\\msbuild.exe.
But for Visual Studio 2017RC the path
Microsoft have created a tool to find the location of Visual Studio 2017 and newer https://github.com/Microsoft/vswhere
That option and newer are decribed in this blog post.