Build Issue due to $(Platform) value

We are facing build issue when we try to build .net project in custom project configuration, like Debug configuration we have added LinuxDebug as a configuration in project to target it for corss platform. But when we try to build using that configuration we are getting dependent project dll not found issue as its looking in different directory. In project file we have mentioned following <OutputPath>$(SolutionDir)\Output\bin$(Platform)$(Configuration)</OutputPath> the refered project is looking that dll in wrong directory, because somehow $(Platform) gets AnyCPU value, but at project level we have mentioned x64. we are not sure where exactly AnyCPU value gets assigned to $(Platform) referred/dependent dll is there in x64 directory. Can someone please help me here