Pass a build_id object to filename__read_build_id function, so it can
populate the size of the build_id object.

Changing filename__read_build_id() code for both ELF/non-ELF code.
Signed-off-by: NJiri Olsa <jolsa@kernel.org>
Acked-by: NIan Rogers <irogers@google.com>
Link: https://lore.kernel.org/r/20201013192441.1299447-3-jolsa@kernel.orgSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>