I found this question as my PATH variable did not contain a reference to MSBuild.exe. In case anyone else is having this issue, my resolution was to explictly register the environment variables for Visual Studio tools from the command prompt:
"%VS100COMNTOOLS%"\\vsvars32.bat // VS2010 environment variables
"%VS110COMNTOOLS%"\\vsvars32.bat // VS2012 environment variables
"%VS120COMNTOOLS%"\\vsvars32.bat // VS2013 environment variables
MSBuild.exe is now registered in PATH
where msbuild
C:\Windows\Microsoft.NET\Framework\v4.0.30319\MSBuild.exe
C:\Windows\Microsoft.NET\Framework\v3.5\MSBuild.exe