Hi @hc-robotics, welcome to the forum! 
In our latest Ping Viewer release we changed from using qmake to cmake, but it seems like our build documentation hasn’t been updated to reflect that. @patrickelectric should be able to provide updated build instructions, but if this is urgent then you should be able to git checkout a commit from before the cmake change and build that with qmake.
From a quick look at the ping-viewer commit history it seems like a36979d is the latest commit from before cmake changes were introduced, but it may be necessary to try an earlier one, and I haven’t tried building PingViewer on RPi so can’t guarantee it will work at all. Would recommend waiting for Patrick if possible
I’ve just added an issue on GitHub to update our Ping Viewer build docs: