VMR Stage2 failing to find NuGet Packages

[Winniexu01]

The Stage 2 builds are failing to find NuGet Packages because no NuGet Packages be published as pipeline artifacts.

This Failing build (internal Microsoft link) is caused by dotnet/sdk#43288:

Copy Previous Build (CentOSStream9_Online_MsftSdk_x64 - NuGet Packages) failed with below error message:

##[error]Error: Not found SourceFolder: /mnt/vss/_work/1/CentOSStream9_Online_MsftSdk_x64_Artifacts/packages'

Only 3 files be downloaded in Download Previous Build (CentOSStream9_Online_MsftSdk_x64) step:

Minimatch patterns: [**/Private.SourceBuilt.Artifacts.*.tar.gz,**/dotnet-sdk-*.tar.gz,**/*.nupkg]
Filtered 3 files from the Minimatch filters supplied.

[MichaelSimons]

@directhex - The changes in dotnet/sdk#43288 broke source-build. It looks as though the two copy steps will need to be conditioned based on the existence of the source folder. It would be nice to not even see the Copy Previous Build (${{ reuseBuildArtifacts }} - Source Build artifacts) step in non-source build legs and similarly not see the Copy Previous Build (${{ reuseBuildArtifacts }} - NuGet Packages) in source-build legs.