Wire up nuspec-based pack to deterministic mode

When building nuspec-based packages, the deterministic-mode
configuration is not flowed correctly to the PackageBuilder class (which
is initialized using this PackArgs object). Seems like this was missed
from the initial deterministic support in
#2989.

This commit is a no-op until deterministic mode is enabled and
NuGet/Home#8601 is fixed.

Author: omajid

src/NuGet.Core/NuGet.Build.Tasks.Pack/PackTaskLogic.cs

@@ -42,6 +42,7 @@ public PackArgs GetPackArgs(IPackTaskRequest<IMSBuildItem> request)
                 BasePath = request.NuspecBasePath,
                 NoPackageAnalysis = request.NoPackageAnalysis,
                 NoDefaultExcludes = request.NoDefaultExcludes,
+                Deterministic = request.Deterministic,
                 WarningProperties = WarningProperties.GetWarningProperties(request.TreatWarningsAsErrors, request.WarningsAsErrors, request.NoWarn, request.WarningsNotAsErrors),
                 PackTargetArgs = new MSBuildPackTargetArgs()
             };