Fix MSBuild property name for Microsoft.Build.Tasks.Core

[eerhardt]

There was a missing 's', which caused source-build to use a pre-built when building.

Related to dotnet/source-build#2412

[MichaelSimons]

LGTM. Should this target release/6.0 instead?

[eerhardt]

Should this target release/6.0 instead?

My understanding is that aspnetcore works like runtime. The process is get a change into main first, make sure it is stable, then port to the release branch.

[dougbu]

/fyi I enabled auto-squish for this PR

[dougbu]

How necessary and urgent in 'release/6.0' is this fix @eerhardt @dseefeld @MichaelSimons❔ And, are we peeling an onion here or is this likely the last source-build fix needed❔

Suggest tell-mode if we do this in 'release/6.0'. Agree @Pilchie❔

[Pilchie]

Yes, tell-mode is fine for 6.0.

[MichaelSimons]

How necessary and urgent in 'release/6.0' is this fix

This is required for .NET 6.0.

are we peeling an onion here?

Yes, we know there are a number of prebuilts in aspnetcore right now (3 direct and 9 indirect). We are still investigating and it is unknown how many will require aspnetcore source changes.

[dougbu]

Alright. Nothing here will break non-source-build builds and we might as well move through the onion incrementally. @dotnet/aspnet-build if any of you have had success using the backport action, please do the needful here.