Due to a problem in the Quartus® Prime software version 16.1, you may see this error in the SDK for OpenCL compiler. This error occurs because Qsys is not set on the PATH by default.
To work around this problem, set the the path to your Qsys directory
For Windows,
set PATH=%PATH%;<path_to_your_quartus_installation_dir>\qsys\bin
For Linux,
export PATH=$PATH:<path_to_your_quartus_installation_dir>/qsys/bin
This problem has been fixed beginning with version 16.1 Update 1 od the Quartus Prime software.