This is a follow-up to my prior post on generating MSBuild files from Solution files.
Sometimes it is important to stop MSBuild from writing the xxx.sln.cache file to the solution folder during a run. This is usually a case where you want to build two flavors of the solution concurrently or you want to keep your source tree clean. To workaround, you can set an environment variable to disable this behavior.
From the MSBuild Team's blog.