[x64] error CS0433 in x64_checked_ubuntu_corefx

[VincentBu]

Job:
https://ci.dot.net/job/dotnet_coreclr/job/master/view/x64/job/jitstress/job/x64_checked_ubuntu_corefx_baseline/826/

Log:

DebugViewTests.cs(484,95): error CS0433: The type 'Environment' exists in both 'System.Runtime.Extensions, Version=4.2.1.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' and 'System.Private.CoreLib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e' 

[BruceForstall]

The next run doesn't show this failure (but does have a timeout in System.Threading.Tasks.Tests.AsyncTaskMethodBuilderTests.AsyncMethodsDropsStateMachineAndExecutionContextUponCompletion)

cc @danmosemsft

[BruceForstall]

@danmosemsft @jkotas I just saw this message again, with a live corefx sync and relatively older coreclr build (compared to this bug). Was this a transient issue that was fixed in the last 24 hours?

[BruceForstall]

Well, maybe this dotnet/coreclr#22106

[jkotas]

Right, this is the type of transient issue that will be addressed by https://github.com/dotnet/corefx/issues/34957#issuecomment-459415999