perf tools: Pass full path of FEATURES_DUMP

When building with an external FEATURES_DUMP, bpf complains
that features dump file is not found. Fix it by passing full file path.

Signed-off-by: David Carrillo-Cisneros <davidcc@google.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Paul Turner <pjt@google.com>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/r/20170827075442.108534-7-davidcc@google.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>