Current perf test code tries to execute python version 2 in order to
test attributes on perf_event_open syscall.  However it's not default
python version anymore a system can have python v3 only or v2 with a
different name (e.g. python2).  So if there's no such python interpreter
with the name 'python', the test would fail like this (yes, it's
happened on my new archlinux laptop :).

13: struct perf_event_attr setup                 🇸🇭 python: command not found
 FAILED!

As we can pass name of the python interpreter on make, use it for
the attr test also.
Signed-off-by: NNamhyung Kim <namhyung@kernel.org>
Acked-by: NJiri Olsa <jolsa@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1355729101-31317-1-git-send-email-namhyung@kernel.org
[ committer note: Added the same mechanism to the python binding test ]
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

It just will add the O= builddir to PYTHONPATH and try to 'use perf',
which will, in verbose mode show the python backtrace with the missing
symbols, such as in the problem fixed in the patch after this one:

  # perf test -v 15
  15: Try 'use perf' in python, checking link problems       :
  --- start ---
  Traceback (most recent call last):
    File "<stdin>", line 1, in <module>
  ImportError: /home/acme/git/build/perf//python/perf.so: undefined symbol: test_attr__enabled
  ---- end ----
  Try 'use perf' in python, checking link problems: FAILED!
  #

Loooong overdue, done.

Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-zmd2oq9gz6t1u145ub7qm2nv@git.kernel.orgSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>