RFC: toolchain for building eBPF modules within the OpenWrt build system

[Florian Eckert]

>> I'd suggest to require a preinstalled host toolchain for the time 
>> being.
> How about requiring a preinstalled host toolchain by default, but
> building it from source on buildbot?

I wouldn't make it dependent on whether openwrt compiles on the buildbot 
or not.
I am not using this build option CONFIG_BUILDBOT on my own builds.
Either use llvm from the buildhost (distribution), or let the openwrt 
buildsystem build its own llvm in the tool directory as you suggest.

@nbd thank you for looking at this, would have needed the ebpf before 
:-)