Removing unused 'isSystem' local that's currently breaking the build. (changeset 1404204)

src/Compilers/CSharp/Test/CommandLine/CommandLineTests.cs

@@ -3590,8 +3590,7 @@ public void BinaryFileErrorTest()
         public void Bug15538()
         {
             // Several Jenkins VMs are still running with local systems permissions.  This suite won't run properly
-            // in that environment.  Removing this check is being tracked by issue #79.  
-            bool isSystem;
+            // in that environment.  Removing this check is being tracked by issue #79.
             using (var identity = System.Security.Principal.WindowsIdentity.GetCurrent())
             {
                 if (identity.IsSystem)