Why does Nios® II processor software fail to build using Windows Subsystem for Linux (WSL) with Ubuntu 18.04.5?

This problem may be seen in any Quartus® Prime Software version when building the Nios® II processor using WSL with Ubuntu 18.04.5.

This is due to different return value when running the command “wslpath -u .” in Nios® II Command Shell.

• Working: The command returns “.”
• Failing: The command returns “wslpath: .”

The returned string of “wslpath: .” breaks the Nios® II software build flow.

Run “wslpath -u .” in Nios® II Command Shell. If the return string is “wslpath: .”, implement any of the following workarounds:

• Use Ubuntu version older than 18.04.5.
• Provide the full BSP directory path to the BSP_DIR in both create-this-bsp and create-this-app scripts.