Move CommandCreationException to root

src/dotnet/CommandCreationException.cs

@@ -0,0 +1,16 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace Microsoft.DotNet.Cli
+{
+    internal class CommandCreationException : Exception
+    {
+        public int ExitCode { get; private set; }
+
+        public CommandCreationException(int exitCode)
+        {
+            ExitCode = exitCode;
+        }
+    }
+}

src/dotnet/commands/dotnet-build/Program.cs

@@ -142,15 +142,5 @@ namespace Microsoft.DotNet.Tools.Build
         {
             return GetProcessStartInfo().Execute();
         }
-
-        private class CommandCreationException : Exception
-        {
-            public int ExitCode { get; private set; }
-
-            public CommandCreationException(int exitCode)
-            {
-                ExitCode = exitCode;
-            }
-        }
     }
 }