Cleaning up artifacts from bootstrap build fails and causes MSB3021 in the actual build later

```
Cleaning up artifacts from bootstrap build...
Remove-Item : Cannot remove item C:\git\dotnet\src\runtime\artifacts\bin\ILLink.Tasks\Release\net\ILLink.Tasks.dll:
Access to the path 'ILLink.Tasks.dll' is denied.
At C:\git\dotnet\src\runtime\eng\build.ps1:403 char:3
+ Remove-Item -Recurse "$PSScriptRoot/../artifacts/bin"
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : PermissionDenied: (ILLink.Tasks.dll:FileInfo) [Remove-Item], UnauthorizedAccessException
+ FullyQualifiedErrorId : RemoveFileSystemItemUnAuthorizedAccess,Microsoft.PowerShell.Commands.RemoveItemCommand
Remove-Item : Directory C:\git\dotnet\src\runtime\artifacts\bin\ILLink.Tasks\Release\net cannot be removed because it
is not empty.
At C:\git\dotnet\src\runtime\eng\build.ps1:403 char:3
+ Remove-Item -Recurse "$PSScriptRoot/../artifacts/bin"
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : WriteError: (net:DirectoryInfo) [Remove-Item], IOException
+ FullyQualifiedErrorId : DirectoryNotEmpty,Microsoft.PowerShell.Commands.RemoveItemCommand

Remove-Item : Directory C:\git\dotnet\src\runtime\artifacts\bin\ILLink.Tasks\Release cannot be removed because it is
not empty.
At C:\git\dotnet\src\runtime\eng\build.ps1:403 char:3
+ Remove-Item -Recurse "$PSScriptRoot/../artifacts/bin"
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : WriteError: (Release:DirectoryInfo) [Remove-Item], IOException
+ FullyQualifiedErrorId : DirectoryNotEmpty,Microsoft.PowerShell.Commands.RemoveItemCommand

Remove-Item : Directory C:\git\dotnet\src\runtime\artifacts\bin\ILLink.Tasks cannot be removed because it is not empty.
At C:\git\dotnet\src\runtime\eng\build.ps1:403 char:3
+ Remove-Item -Recurse "$PSScriptRoot/../artifacts/bin"
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : WriteError: (ILLink.Tasks:DirectoryInfo) [Remove-Item], IOException
+ FullyQualifiedErrorId : DirectoryNotEmpty,Microsoft.PowerShell.Commands.RemoveItemCommand

Remove-Item : Cannot remove item C:\git\dotnet\src\runtime\artifacts\bin\installer.tasks\Release\installer.tasks.dll:
Access to the path 'installer.tasks.dll' is denied.
At C:\git\dotnet\src\runtime\eng\build.ps1:403 char:3
+ Remove-Item -Recurse "$PSScriptRoot/../artifacts/bin"
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : PermissionDenied: (installer.tasks.dll:FileInfo) [Remove-Item], UnauthorizedAccessExcept
ion
+ FullyQualifiedErrorId : RemoveFileSystemItemUnAuthorizedAccess,Microsoft.PowerShell.Commands.RemoveItemCommand
Remove-Item : Directory C:\git\dotnet\src\runtime\artifacts\bin\installer.tasks\Release cannot be removed because it
is not empty.
At C:\git\dotnet\src\runtime\eng\build.ps1:403 char:3
+ Remove-Item -Recurse "$PSScriptRoot/../artifacts/bin"
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : WriteError: (Release:DirectoryInfo) [Remove-Item], IOException
+ FullyQualifiedErrorId : DirectoryNotEmpty,Microsoft.PowerShell.Commands.RemoveItemCommand

Remove-Item : Directory C:\git\dotnet\src\runtime\artifacts\bin\installer.tasks cannot be removed because it is not
empty.
At C:\git\dotnet\src\runtime\eng\build.ps1:403 char:3
+ Remove-Item -Recurse "$PSScriptRoot/../artifacts/bin"
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : WriteError: (installer.tasks:DirectoryInfo) [Remove-Item], IOException
+ FullyQualifiedErrorId : DirectoryNotEmpty,Microsoft.PowerShell.Commands.RemoveItemCommand

Remove-Item : Directory C:\git\dotnet\src\runtime\artifacts\bin cannot be removed because it is not empty.
At C:\git\dotnet\src\runtime\eng\build.ps1:403 char:3
+ Remove-Item -Recurse "$PSScriptRoot/../artifacts/bin"
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : WriteError: (C:\git\dotnet\src\runtime\artifacts\bin:DirectoryInfo) [Remove-Item], IOExc
eption
+ FullyQualifiedErrorId : DirectoryNotEmpty,Microsoft.PowerShell.Commands.RemoveItemCommand
```

This then results in the following errors later:
```
C:\git\dotnet\.dotnet\sdk\11.0.100-alpha.1.26060.102\Microsoft.Common.CurrentVersion.targets(4917,5): error MSB3026: Could not copy "C:\git\dotnet\src\runtime\artifacts\obj\installer.tasks\Release\installer.tasks.dll" to "C:\git\dotnet\src\runtime\artifacts\bin\installer.tasks\Release\installer.tasks.dll". Beginning retry 1 in 1
000ms. The process cannot access the file 'C:\git\dotnet\src\runtime\artifacts\bin\installer.tasks\Release\installer.tasks.dll' because it is being used by another process. The file is locked by: ".NET Host (25364)" [C:\git\dotnet\src\runtime\src\tasks\installer.tasks\installer.tasks.csproj]
```

@jkoritzinsky