These files are produced when Incremental Link-Time Code Generation (LTCG) is enabled. This is a new feature in Visual C++ 2015.
If you disable Incremental LTCG, the linker will stop producing these files. But then you lose the benefits of Incremental LTCG.
To disable Incremental LTCG, modify your project properties: Under Linker => Optimization change “Link Time Code Generation” to something other than “Use Fast Link Time Code Generation (/LTCG:incremental)” (this is the default for Release builds).