Fix test.

Author: timcassell

src/BenchmarkDotNet/Toolchains/ToolchainExtensions.cs

@@ -27,14 +27,15 @@ private static IToolchain GetToolchain(Job job, Descriptor descriptor)
                 ? toolchain
                 : GetToolchain(
                     job.ResolveValue(EnvironmentMode.RuntimeCharacteristic, EnvironmentResolver.Instance),
-                    descriptor);
+                    descriptor,
+                    job.HasValue(InfrastructureMode.NuGetReferencesCharacteristic) || job.HasValue(InfrastructureMode.BuildConfigurationCharacteristic));
 
-        internal static IToolchain GetToolchain(this Runtime runtime, Descriptor descriptor = null)
+        internal static IToolchain GetToolchain(this Runtime runtime, Descriptor descriptor = null, bool preferMsBuildToolchains = false)
         {
             switch (runtime)
             {
                 case ClrRuntime clrRuntime:
-                    if (RuntimeInformation.IsFullFramework &&
+                    if (!preferMsBuildToolchains && RuntimeInformation.IsFullFramework &&
                         // If dotnet SDK is not installed, we use RoslynToolchain (CsProjClassicNetToolchain currently does not support custom cli path).
                         (!HostEnvironmentInfo.GetCurrent().IsDotNetCliInstalled()
                         // Integration tests take too much time, because each benchmark run rebuilds the test suite and BenchmarkDotNet itself.

tests/BenchmarkDotNet.IntegrationTests/NugetReferenceTests.cs

@@ -21,7 +21,7 @@ public NuGetReferenceTests(ITestOutputHelper output) : base(output)
         [FactEnvSpecific("For some reason this test is unstable on Ubuntu for both AzureDevOps and Travis CI", EnvRequirement.NonLinux)]
         public void UserCanSpecifyCustomNuGetPackageDependency()
         {
-            var toolchain = RuntimeInformation.GetCurrentRuntime().GetToolchain();
+            var toolchain = RuntimeInformation.GetCurrentRuntime().GetToolchain(preferMsBuildToolchains: true);
 
             var job = Job.Dry.WithToolchain(toolchain).WithNuGet("Newtonsoft.Json", "13.0.2");
             var config = CreateSimpleConfig(job: job);