kbuild: Unify options for BTF generation for vmlinux and modules

stable inclusion
from stable-v5.10.151
commit c5006abb80e276896ff7237300a6d447708c7924
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I64L0X

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c5006abb80e276896ff7237300a6d447708c7924



--------------------------------

commit 9741e07e upstream.

[skipped --btf_gen_floats option in pahole-flags.sh, skipped
Makefile.modfinal change, because there's no BTF kmod support,
squashing in 'exit 0' change from merge commit fc02cb2b]

Using new PAHOLE_FLAGS variable to pass extra arguments to
pahole for both vmlinux and modules BTF data generation.

Adding new scripts/pahole-flags.sh script that detect and
prints pahole options.

[ fixed issues found by kernel test robot ]

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20211029125729.70002-1-jolsa@kernel.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Lipeng Sang <sanglipeng1@jd.com>