Moving feature checks code under tools/build directory.

Changing also $feature_dir to point to new feature directory location
and perf Makefiles to include Makefile.feature from new location.
Signed-off-by: NJiri 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-3lamtb30dhf4wo99y1n8kxg0@git.kernel.orgSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/n/tip-wicrcLCy2wkalka7iwsuzgpb@git.kernel.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>

Start the split-out of the feature check code by adding a list of features to be
tested, and rules to process that list by building its matching feature-check
file in config/feature-checks/test-<feature>.c.

Add 'hello' as the initial feature.

This structure will allow us to build split-out feature checks in parallel and
thus speed up feature detection dramatically.

No change in functionality: no feature check is used by the build rules yet.

Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/n/tip-pixkihgscFaohfFigq5yt9gs@git.kernel.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>