Build fails for echo-sockmap target

Hi
I am trying to build echo-sockmap target and it fails since echo-sockmap-ebpf.c is not in the repo (it is in the .gitignore and probably was not pushed)
If I try to remove this file from Makefile I get

2019-02-tcp-splice/echo-sockmap.c:43: undefined reference to `bpf_reloc_prog_verdict'
2019-02-tcp-splice/echo-sockmap.c:43: undefined reference to `bpf_insn_prog_verdict'
2019-02-tcp-splice/echo-sockmap.c:48: undefined reference to `bpf_insn_prog_parser_cnt'
2019-02-tcp-splice/echo-sockmap.c:48: undefined reference to `bpf_insn_prog_parser'
2019-02-tcp-splice/echo-sockmap.c:57: undefined reference to `bpf_insn_prog_verdict_cnt'
2019-02-tcp-splice/echo-sockmap.c:57: undefined reference to `bpf_insn_prog_verdict'

Please advise. Thanks!