I have a Linksys E1200 I got for real cheap a few years back and am going to make a hackme project from it. First step - get a build environment working.
I'm not sure why a container-based build isn't the default recommendation on the dd-wrt or OpenWrt forums. But here's mine:
@finity we're usually doing --mount for bind-mounts these days
Cross-compile build environs usually screw up my normal host environ more than I like, and compete with each other, so I'm putting it in a container.