Compilation error: bad path in base.sdc

I believe the base.sdc file is provided by your BSP. Search your BSP folder. If that file is there, and that hardcoded path also exists in the copy inside the BSP, then the problem is from the BSP. The manufacturer could have incorrectly hardcoded the path, expecting people to install Quartus in the default path. You might be able to manually fix the BSP by editing that file and correcting the path to point to your actual installation directory; however, you should probably still report it to the manufacturer so that they would fix it.