selftests/bpf: fix broken build, take 2

selftests/bpf: fix broken build, take 2

Merge of 'linux-kselftest-4.11-rc1':

1. Partially removed use of 'test_objs' target, breaking force rebuild of
BPFOBJ, introduced in commit be753f75c1d8 ("bpf: Rebuild bpf.o for any
dependency update").

  Update target so dependency on BPFOBJ is restored.

2. Introduced commit 40d35d994e79 ("selftests: Fix the .c linking rule")
which fixes order of LDLIBS.

  Commit ffc9d42a9306 ("bpf: Always test unprivileged programs") added
libcap dependency into CFLAGS. Use LDLIBS instead to fix linking of
test_verifier.

3. Introduced commit 8b7eb2fcdfd0 ("selftests: Fix selftests build to
just build, not run tests").

  Reordering the Makefile allows us to remove the 'all' target.

Tested both:
    selftests/bpf$ make
and
    selftests$ make TARGETS=bpf
on Ubuntu 16.04.2.

Signed-off-by: Zi Shen Lim <zlim.lnx@gmail.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Tested-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Tested-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Shuah Khan <shuahkh@osg.samsung.com>
Signed-off-by: David S. Miller <davem@davemloft.net>