Single one as in specific for you device? Choose target system, possible subtarget and then your device. Then it'll build a toolchain used for that device.
Yes, looking for the one just for my device as listed above.
OK, I did try that before and it still appeared to build multiple ones, so I stopped it and thought I would ask here first incase I could get it to build just the one.
Have started it again now, so will see what it turns out.
You should not be looking under build_dir/ for the toolchain. Those are working directories used during building the target and toolchain packages, respectively. Packaged toolchain goes under bin/targets/...
As to the toolchain type you may want to investigate settings under
Advanced configuration options (for developers) ->Toolchain Options
Googling around and that uClibc version refers to something that was released in 2012. I would be surprised if you could pull out something like that with current OpenWrt. Your best bet could be to try to turn back time and find OpenWrt version that used uClibc or to build your own uClibc based toolchain with instructions from here.
uClibc 0.9.33.2 support has been removed from OpenWrt in 2015, well before GCC 10 was released in 2020.
They have never been supported in OpenWrt at the same time.
If you have stumbled upon that combo, it is somebody's private development. (Some OEM that has bumped an ancient OpenWrt codebase (pre-2015) to use the brand new GCC version ???)
Thank you both for your replies. That all makes a little more sense now. I should have googled the age of that uClibc version myself actually, makes a bit more sense why I couldn't get OpenWrt to build it.
I will have a look at the instructions that sandberg has linked too, and hopefully get something together there.