libperf: Add build version support

libperf: Add build version support

Add a shared library version, generating the following files:

  $ ll tools/perf/lib/libperf.so*
  libperf.so -> libperf.so.0.0.1
  libperf.so.0 -> libperf.so.0.0.1
  libperf.so.0.0.1

Committer testing:

One has to build just libbperf to get this, building perf so far doesn't
trigger this, i.e. I tried:

  $ make O=/tmp/build/perf -C tools/perf

And the files above were not created, so one has to do:

  $ make O=/tmp/build/perf -C tools/perf/lib/
  make: Entering directory '/home/acme/git/perf/tools/perf/lib'
    LINK     /tmp/build/perf/libperf.so.0.0.1
  make: Leaving directory '/home/acme/git/perf/tools/perf/lib'
  $ ls -la /tmp/build/perf/*.so.*
  lrwxrwxrwx. 1 acme acme    16 Jul 22 15:37 /tmp/build/perf/libperf.so.0 -> libperf.so.0.0.1
  -rwxrwxr-x. 1 acme acme 16368 Jul 22 15:37 /tmp/build/perf/libperf.so.0.0.1
  $

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexey Budankov <alexey.budankov@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20190721112506.12306-25-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>