perf tools: Add an option to build without libbfd

perf tools: Add an option to build without libbfd

Some distributions, like debian, don't link perf with libbfd. Add a
build flag to make this configuration buildable and testable.

This was inspired by:

  https://lore.kernel.org/linux-perf-users/20210910102307.2055484-1-tonyg@leastfixedpoint.com/T/#u

Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: tony garnock-jones <tonyg@leastfixedpoint.com>
Link: http://lore.kernel.org/lkml/20210910225756.729087-1-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>