We are in the process of setting up builds for delphi projects, is there a way to only install Delphi 10.2 command line compiler on the build server which will be used only for building delphi projects using VSTS builds.
Delphi installation package doesn't have such option. Install full version, use command line compiler only. You don't need extra license and probably don't even need to activate (but it is allowed as long as you use command line tools for unattended builds only). Licensing issue discussed here: Is a separate Delphi XE4 license required for a build machine?