Disable ebpf plugin as in OpenWrt there is no package libbpf.
- With that, I need to introduce patch, which is not merged into netdata,
yet. Without it, I still got during cross-compilation this error:
checking for externaldeps/libbpf/libbpf.a... configure: error: cannot check for file existence when cross compiling

- And yes, the flag was there.

Signed-off-by: Josef Schlehofer <pepe.schlehofer@gmail.com>