perf python: Make clang_has_option() work on Python 3

perf python: Make clang_has_option() work on Python 3

Use a bytes literal so it works with Python 3's version of Popen().
Note that the b"..." syntax requires Python 2.6+.

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/r/20181005204058.7966-2-ehabkost@redhat.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>