How to specify MSbuild output folder?

I know the docs say otherwise, but try OutputPath instead of OutDir.

For Delphi projects you need to use DCC_ExeOutput to specify where the EXE should go.

C:\MyProjects>MSbuild "C:\MyTestProject\Test.dproj" /t:Build /p:DCC_ExeOutput="C:\Output\bin\"

Take a look inside Test.dproj for any other options you might want to specify.