MSBuild response files
Response (.rsp) files are text files that contain MSBuild.exe command-line switches. Each switch can be on a separate line or all switches can be on one line. Comment lines are prefaced with a # symbol. The @ switch is used to pass another response file to MSBuild.exe.
MSBuild.rsp
The autoresponse file is a special .rsp file that MSBuild.exe automatically uses when building a project. This file, MSBuild.rsp, must be in the same directory as MSBuild.exe, otherwise it will not be found. You can edit this file to specify default command-line switches to MSBuild.exe. For example, if you use the same logger every time you build a project, you can add the -logger switch to MSBuild.rsp, and MSBuild.exe will use the logger every time a project is built.
Directory.Build.rsp
In version 15.6 and above, MSBuild will search parent directories of the project for a file named Directory.Build.rsp. This can be helpful in a source code repository to provide default arguments during command-line builds. It can also be used to specify the command-line arguments of hosted builds.