Possible incorrect use of "NOT ... OR ..." pattern

[GrabYourPitchforks]

Our internal tools are flagging these blocks of code as potentially improper use of the not ... or ... pattern matching syntax.

arcade/src/Microsoft.DotNet.Build.Tasks.Feed/src/PublishArtifactsInManifestBase.cs

Line 757 in 23d4316

FrozenSet<string> excludeFiles = files.Where(x => x is not null or "").ToFrozenSet();

See dotnet/roslyn#75506 for more information on why this pattern is being flagged. If this logic is correct, consider restructuring it to use clarifying () parentheses.