I want to build projects from the command line. Is it possible to deploy a C# compiler without installing Visual Studio?
Yes, if you have the .NET SDK, it's there. For example,
C:\WINDOWS\Microsoft.NET\Framework\v[your version number]\csc.exe
msbuild.exe should be there too, and you can use that to build project (.csproj) files.
msbuild.exe
.csproj