tools build: Pass libbpf feature only if libbpf 1.0+

libbpf 1.0 represented a cleanup and stabilization of APIs. Simplify
development by only passing the feature test if libbpf 1.0 is installed.

Committer notes:

Change 'make -C tools/perf build-test' so that the LIBBPF_DYNAMIC=1 test
runs only if libbpf is >= 1.0.

Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andres Freund <andres@anarazel.de>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Christy Lee <christylee@fb.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Quentin Monnet <quentin@isovalent.com>
Cc: Roberto Sassu <roberto.sassu@huawei.com>
Cc: bpf@vger.kernel.org
Link: https://lore.kernel.org/r/20230116010115.490713-2-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

perf tools: Allow to link with libbpf dynamicaly

Currently we support only static linking with kernel's libbpf
(tools/lib/bpf). This patch adds libbpf package detection and support to
link perf with it dynamically.

The libbpf package status is displayed with:

$ make VF=1
Auto-detecting system features:
...
... libbpf: [ on ]

It's not checked by default, because it's quite new. Once it's on most
distros we can switch it on.

For the same reason it's not added to the test-all check.

Perf does not need advanced version of libbpf, so we can check just for
the base bpf_object__open function.

Adding new compile variable to detect libbpf package and link bpf
dynamically:

$ make LIBBPF_DYNAMIC=1
...
LINK perf
$ ldd perf | grep bpf
libbpf.so.0 => /lib64/libbpf.so.0 (0x00007f46818bc000)

If libbpf is not installed, build stops with:

Makefile.config:486: *** Error: No libbpf devel library found,\
please install libbpf-devel. Stop.

Committer testing:

$ make LIBBPF_DYNAMIC=1 -C tools/perf O=/tmp/build/perf
make: Entering directory '/home/acme/git/perf/tools/perf'
BUILD: Doing 'make -j8' parallel build
Makefile.config:493: *** Error: No libbpf devel library found, please install libbpf-devel. Stop.
make[1]: *** [Makefile.perf:225: sub-make] Error 2
make: *** [Makefile:70: all] Error 2
make: Leaving directory '/home/acme/git/perf/tools/perf'
$

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Toke Høiland-Jørgensen <toke@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Andrii Nakryiko <andriin@fb.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Martin KaFai Lau <kafai@fb.com>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <songliubraving@fb.com>
Cc: Yonghong Song <yhs@fb.com>
Cc: bpf@vger.kernel.org
Cc: netdev@vger.kernel.org
Link: http://lore.kernel.org/lkml/20191126121253.28253-1-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>