reproducible OpenWrt: To not depend on the host LLVM add some lines to the...

reproducible OpenWrt: To not depend on the host LLVM add some lines to the .config seed to build LLVM for eBPF from source.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>
Signed-off-by: Holger Levsen <holger@layer-acht.org>