perf build: Make features checks directory configurable

perf build: Make features checks directory configurable

Putting feature checks directory into $feature_dir, so it's easy to
configure when we move it to bools/build later.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: David Ahern <david.ahern@oracle.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-sq2nsds6uk93372iyxcqcf6q@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>