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.
The auto-response 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.
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.