perf build: Fix single target build dependency check

Currently if we build a single target like:

  $ touch util/map.c && make util/map.o

It will not rebuild util/map.o if it already exists and util/map.c is
modified.

The reason is that the top-level 'Makefile' processes util/map.o as an
implicit rule and if util/map.o exists make considers the 'util/map.o'
target as done and will not nest into Makefile.perf.

Adding FORCE for '%', because that's what we want to nest into
Makefile.perf for any target.

Adding Makefile into phony targets, because make tries to rebuild it and
it's also resolved as '%' target.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Lukas Wunner <lukas@wunner.de>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/r/1434977452-32520-4-git-send-email-jolsa@kernel.org


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