[release/6.0.1xx] dotnet/runtime: Disable package validation in source-build for reliability

[dagood]

• To fix this flakiness: 6.0 dotnet/runtime: Microsoft.DotNet.Compatibility.ValidatePackage fails, "System.MissingMethodException: Method not found: '...'" source-build#2501
• Upstream PR: [release/6.0] Disable package validation in source-build for reliability runtime#60881

@omajid Can you check if this fixes it the same way as the workaround you mentioned you've been using?

Hoping that getting this merged will avoid having to add a patch for it in each Linux distro. (Or otherwise causing builds to be flaky.)

[omajid]

@omajid Can you check if this fixes it the same way as the workaround you mentioned you've been using?

I tried multiple builds overnight and the failures I was seeing earlier are now gone with this change.

[MichaelSimons]

Was hoping the runtime fix would flow but it hasn't yet and this is hindering dev workflows. Merging.