Fix the symlink creation from r249484 so that repeated installs work correctly.
Fix the symlink creation from r249484 so that repeated
installs work correctly.

Suggested by Tijl Coosemans.

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