aspnetcore: 'The process cannot access the file' during CI build sometimes

This has been happening a few times recently. It’s odd because BlazorTemplates.Tests doesn’t depend on Microsoft.DotNet.Web.Spa.ProjectTemplates so it shouldn’t be copying it anywhere.

There is some custom msbuild logic being invoked right before the error: https://github.com/dotnet/aspnetcore/blob/main/src/ProjectTemplates/TestInfrastructure/PrepareForTest.targets So maybe that has something to do with it. We might just need to add /bl to this part of the build temporarily.

Example build: https://dev.azure.com/dnceng/public/_build/results?buildId=1106179&view=logs&j=48c285a2-daf4-5ecb-cb99-42232769ca29&t=73646f8d-7520-5361-e1ad-d9d207b2cd21

./src/ProjectTemplates/build.sh --ci --nobl --pack --no-restore --no-build-deps
========================== Starting Command Output ===========================
/bin/bash --noprofile --norc /datadisks/disk1/workspace/_work/_temp/7404866d-8c11-4324-8bfe-b62b36813c80.sh
  RepoTasks -> /datadisks/disk1/workspace/_work/1/s/artifacts/bin/RepoTasks/Release/net6.0/RepoTasks.dll
  Successfully created package '/datadisks/disk1/workspace/_work/1/s/artifacts/packages/Release/Shipping/Microsoft.DotNet.Web.Client.ItemTemplates.6.0.0-ci.nupkg'.
  Successfully created package '/datadisks/disk1/workspace/_work/1/s/artifacts/packages/Release/Shipping/Microsoft.DotNet.Web.ItemTemplates.6.0.0-ci.nupkg'.
  Preparing environment for tests
  Removed directory /datadisks/disk1/workspace/_work/1/s/src/ProjectTemplates/BlazorTemplates.Tests/bin/Release/net6.0/TestTemplates/
  Removed directory /datadisks/disk1/workspace/_work/1/s/obj/template-restore/
  Created directory /datadisks/disk1/workspace/_work/1/s/src/ProjectTemplates/BlazorTemplates.Tests/bin/Release/net6.0/TestTemplates/
  Created directory /datadisks/disk1/workspace/_work/1/s/obj/template-restore/
  Successfully created package '/datadisks/disk1/workspace/_work/1/s/artifacts/packages/Release/Shipping/Microsoft.DotNet.Web.ProjectTemplates.6.0.6.0.0-ci.nupkg'.
/datadisks/disk1/workspace/_work/1/s/.dotnet/sdk/6.0.100-preview.4.21222.6/Microsoft.Common.CurrentVersion.targets(4965,5): error MSB3026: Could not copy "/datadisks/disk1/workspace/_work/1/s/artifacts/packages/Release/Shipping/Microsoft.DotNet.Web.Spa.ProjectTemplates.6.0.6.0.0-ci.nupkg" to "bin/Release/net6.0/Microsoft.DotNet.Web.Spa.ProjectTemplates.6.0.6.0.0-ci.nupkg". Beginning retry 1 in 1000ms. The process cannot access the file '/datadisks/disk1/workspace/_work/1/s/artifacts/packages/Release/Shipping/Microsoft.DotNet.Web.Spa.ProjectTemplates.6.0.6.0.0-ci.nupkg' because it is being used by another process.  [/datadisks/disk1/workspace/_work/1/s/src/ProjectTemplates/BlazorTemplates.Tests/BlazorTemplates.Tests.csproj]
##[error].dotnet/sdk/6.0.100-preview.4.21222.6/Microsoft.Common.CurrentVersion.targets(4965,5): error MSB3026: (NETCORE_ENGINEERING_TELEMETRY=Build) Could not copy "/datadisks/disk1/workspace/_work/1/s/artifacts/packages/Release/Shipping/Microsoft.DotNet.Web.Spa.ProjectTemplates.6.0.6.0.0-ci.nupkg" to "bin/Release/net6.0/Microsoft.DotNet.Web.Spa.ProjectTemplates.6.0.6.0.0-ci.nupkg". Beginning retry 1 in 1000ms. The process cannot access the file '/datadisks/disk1/workspace/_work/1/s/artifacts/packages/Release/Shipping/Microsoft.DotNet.Web.Spa.ProjectTemplates.6.0.6.0.0-ci.nupkg' because it is being used by another process. 
  Successfully created package '/datadisks/disk1/workspace/_work/1/s/artifacts/packages/Release/Shipping/Microsoft.DotNet.Web.Spa.ProjectTemplates.6.0.6.0.0-ci.nupkg'.
  Preparing environment for tests
  Removed directory /datadisks/disk1/workspace/_work/1/s/src/ProjectTemplates/test/bin/Release/net6.0/TestTemplates/
  Removed directory /datadisks/disk1/workspace/_work/1/s/obj/template-restore/
  Created directory /datadisks/disk1/workspace/_work/1/s/src/ProjectTemplates/test/bin/Release/net6.0/TestTemplates/
  Created directory /datadisks/disk1/workspace/_work/1/s/obj/template-restore/
  BlazorTemplates.Tests -> /datadisks/disk1/workspace/_work/1/s/src/ProjectTemplates/BlazorTemplates.Tests/bin/Release/net6.0/BlazorTemplates.Tests.dll
  ProjectTemplates.Tests -> /datadisks/disk1/workspace/_work/1/s/src/ProjectTemplates/test/bin/Release/net6.0/ProjectTemplates.Tests.dll