How to clean sources on multiple build agents - tfs

Question

Let's say you have multiple build agents configured and you have a folder on the build agents that has some content in it that isn't from TFS (even specifying Output, some intermediate stuff like the obj folder might be generated in a project folder for example) and you deleted the folder in TFS.
Next time you'd build, you'd get an cannot be deleted because it is not empty. error. When triggering the build, you could add the Build.Clean variable as all or source to your next build to fix it. However, since you have multiple agent, only the next agent running will receive that command and clean, and any other builds you make that falls on another agent will fail again because they still have the folder.
Editing the whole build definition so they do a full clean every build would be overkill.
I am of course looking for something else than "Go in the actual folders and delete the folders manually". If it changes anything, the agents aren't hosted, but on premises.
Edit: Logs from the build server, starting with the last cannot be deleted warning:
2017-03-14T20:23:24.2384009Z d:\vso\b1\_work\32\s\[Obfuscated] cannot be deleted because it is not empty.
2017-03-14T20:23:24.4964210Z ##[error]Exit code 1 returned from process: file name 'tf', arguments 'vc get /version:24617 /recursive /overwrite d:\vso\b1\_work\32\s /loginType:OAuth /login:.,******** /noprompt'.
2017-03-14T20:23:24.5124180Z ##[debug]Microsoft.VisualStudio.Services.Agent.ProcessExitCodeException: Exit code 1 returned from process: file name 'tf', arguments 'vc get /version:24617 /recursive /overwrite d:\vso\b1\_work\32\s /loginType:OAuth /login:.,******** /noprompt'.
at Microsoft.VisualStudio.Services.Agent.ProcessInvoker.<ExecuteAsync>d__19.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.VisualStudio.Services.Agent.Worker.Build.TfsVCCommandManager.<RunCommandAsync>d__26.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.VisualStudio.Services.Agent.Worker.Build.TFCommandManager.<GetAsync>d__15.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.VisualStudio.Services.Agent.Worker.Build.TfsVCSourceProvider.<GetSourceAsync>d__3.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.VisualStudio.Services.Agent.Worker.Build.BuildJobExtension.<PrepareAsync>d__23.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.VisualStudio.Services.Agent.Worker.JobExtensionRunner.<RunAsync>d__30.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.VisualStudio.Services.Agent.Worker.StepsRunner.<RunAsync>d__0.MoveNext()
2017-03-14T20:23:24.5174212Z ##[section]Finishing: Get Sources

Answer 1

Ran into this topic through Google.
We have the same scenario and i tried to explain it here too.
Basically how we now fixed it is we created a new build definition that we use to queue new builds with the Build.Clean = all parameter.
So we have a PowerShell script that loops over all AgentsNames we want to clean and queue a new clean build and add the Demand "Agent.Name -equals agentName".
this way your clean build is queued on all agents you want to clean.