Aha! I suspect the problem is that pesky OneDrive.
Do this:
- File > Preferences > Sketchbook location > set the sketchbook to any convenient folder that is not in the OneDrive
- Click "OK"
- Sketch > Include Library > Manage Libraries
- Wait for download to finish
- In the "Filter your search" box, type "u8glib".
- Scroll down until you see "U8glib by oliver". Click on it.
- Click "Install"
- Wait for installation to finish
- Click "Close"
- Try compiling your Marlin again
The reason you needed to install U8glib again is because it was previously installed to your old sketchbook location and the Arduino IDE does not transfer the contents of your old sketchbook folder when you change to a different one. Everything is still there in your old sketchbook folder (C:\Users\jgsav\OneDrive\Documents\Arduino) so don't worry in case you have anything important in there you can just copy it over to the new sketchbook but I thought it would be best to just reinstall the library to make sure no problems are introduced.