Replace .sinclude by .if exists()/.include/.endif so that older make(1)'s can handle it as well.
Replace .sinclude by .if exists()/.include/.endif so that older make(1)'s can
handle it as well.

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase