Fix Clean build of pkgproj without restore
Fix Clean build of pkgproj without restore

The internal build runs a Clean before restoring packages.
This caused my check for the targets file to be hit during
clean and fail the build.
Move back to an exists check and run a target to make sure
the baseline was imported during build.

[tfs-changeset: 1610501]

ElJerry/wcf,KKhurin/wcf,StephenBonikowsky/wcf,MattGal/wcf,hongdai/wcf,imcarolwang/wcf,dotnet/wcf,mconnew/wcf,shmao/wcf,KKhurin/wcf,iamjasonp/wcf,dotnet/wcf,iamjasonp/wcf,StephenBonikowsky/wcf,ericstj/wcf,dotnet/wcf,imcarolwang/wcf,MattGal/wcf,mconnew/wcf,mconnew/wcf,shmao/wcf,ElJerry/wcf,imcarolwang/wcf,hongdai/wcf,ericstj/wcf,zhenlan/wcf,zhenlan/wcf