Fix BuildAssetsUtilsTests to not depend on host machine envvars

Use SettingsUtility.GetGlobalPackagesFolder with an empty
IEnvironmentVariableReader so the test doesn't pick up the
NUGET_PACKAGES environment variable from the host machine.

Agent-Logs-Url: https://github.com/NuGet/NuGet.Client/sessions/e7319773-b4d6-448e-b48f-96427c36f739

Co-authored-by: nkolev92 <2878341+nkolev92@users.noreply.github.com>

Author: Copilot

test/NuGet.Core.Tests/NuGet.Commands.Test/BuildAssetsUtilsTests.cs

@@ -18,6 +18,7 @@
 using NuGet.Repositories;
 using NuGet.Test.Utility;
 using NuGet.Versioning;
+using Test.Utility;
 using Xunit;
 
 namespace NuGet.Commands.Test
@@ -177,7 +178,7 @@ public void BuildAssetsUtils_ReplaceWithUserProfileMacro()
             // Arrange
             using (var randomProjectDirectory = TestDirectory.Create())
             {
-                var globalPackagesFolder = SettingsUtility.GetGlobalPackagesFolder(NullSettings.Instance);
+                var globalPackagesFolder = SettingsUtility.GetGlobalPackagesFolder(NullSettings.Instance, TestEnvironmentVariableReader.EmptyInstance);
 
                 if (!string.IsNullOrEmpty(globalPackagesFolder))
                 {