Changed default toolchain for .Net Framework to CsProjClassicNetToolchain.

Author: timcassell

src/BenchmarkDotNet/Running/BuildPartition.cs

@@ -80,7 +80,7 @@ internal bool ForcedNoDependenciesForIntegrationTests
         {
             get
             {
-                if (!XUnitHelper.IsIntegrationTest.Value || !RuntimeInformation.IsNetCore)
+                if (!XUnitHelper.IsIntegrationTest.Value)
                     return false;
 
                 var job = RepresentativeBenchmarkCase.Job;

src/BenchmarkDotNet/Toolchains/ToolchainExtensions.cs

@@ -36,7 +36,9 @@ internal static IToolchain GetToolchain(this Runtime runtime, Descriptor? descri
             {
                 case ClrRuntime clrRuntime:
                     if (!preferMsBuildToolchains && RuntimeInformation.IsFullFramework
-                        && RuntimeInformation.GetCurrentRuntime().MsBuildMoniker == runtime.MsBuildMoniker)
+                        && RuntimeInformation.GetCurrentRuntime().MsBuildMoniker == runtime.MsBuildMoniker
+                        // If dotnet SDK is installed, we use CsProjClassicNetToolchain.
+                        && !HostEnvironmentInfo.GetCurrent().IsDotNetCliInstalled())
                     {
                         return RoslynToolchain.Instance;
                     }