Following the steps to build retroarch here.
I followed the steps for subsequent builds since I was updating from 1.6.7 > 1.6.9
On the make -j4 step I ended up getting this message.
make: *** No rule to make target ‘obj-unix/cores/libretro-imageviewer/image_core.o’, needed by ‘retroarch’. Stop.
I believe the error to be around line 303 in Makefile.common
I’m running Windows 10