Don't calculate muxer path in a loop

Author: Youssef1313

src/Cli/dotnet/Commands/Test/TestModulesFilterHandler.cs

@@ -48,10 +48,11 @@ public bool RunWithTestModulesFilter(ParseResult parseResult)
             return false;
         }
 
+        var muxerPath = new Muxer().MuxerPath;
         foreach (string testModule in testModulePaths)
         {
             RunProperties runProperties = testModule.HasExtension(CliConstants.DLLExtension)
-                ? new RunProperties(new Muxer().MuxerPath, $@"exec ""{testModule}""", null)
+                ? new RunProperties(muxerPath, $@"exec ""{testModule}""", null)
                 : new RunProperties(testModule, null, null);
 
             var testApp = new ParallelizableTestModuleGroupWithSequentialInnerModules(new TestModule(runProperties, null, null, true, true, null));