perf bpf: Fix building perf with BUILD_BPF_SKEL=1 by default in more distros

Arnaldo reported that building all his containers with BUILD_BPF_SKEL=1
to then make this the default he found problems in some distros where
the system linux/bpf.h file was being used and lacked this:

   util/bpf_skel/bperf_leader.bpf.c:13:20: error: use of undeclared identifier 'BPF_F_PRESERVE_ELEMS'
           __uint(map_flags, BPF_F_PRESERVE_ELEMS);

So use instead the vmlinux.h file generated by bpftool from BTF info.

This fixed these as well, getting the build back working on debian:11,
debian:experimental and ubuntu:21.10:

  In file included from In file included from util/bpf_skel/bperf_leader.bpf.cutil/bpf_skel/bpf_prog_profiler.bpf.c::33:
  :
  In file included from In file included from /usr/include/linux/bpf.h/usr/include/linux/bpf.h::1111:
  :
  /usr/include/linux/types.h/usr/include/linux/types.h::55::1010:: In file included from  util/bpf_skel/bperf_follower.bpf.c:3fatal errorfatal error:
  : : In file included from /usr/include/linux/bpf.h:'asm/types.h' file not found11'asm/types.h' file not found:

  /usr/include/linux/types.h:5:10: fatal error: 'asm/types.h' file not found
  #include <asm/types.h>#include <asm/types.h>

           ^~~~~~~~~~~~~         ^~~~~~~~~~~~~

  #include <asm/types.h>
           ^~~~~~~~~~~~~
  1 error generated.

Reported-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Song Liu <song@kernel.org>
Tested-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lore.kernel.org/lkml/CF175681-8101-43D1-ABDB-449E644BE986@fb.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>