tools build: Make fixdep a hostprog

It is used in the build process, so stop suppressing its build in tools
cross builds.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Cc: linuxppc-dev@lists.ozlabs.org
Link: http://lkml.kernel.org/r/20160927141846.GA6589@krava


[ Use HOSTCC on the $(OUTPUT)fixdep target, it was using the x-compiler
  to link fixdep-in.o, that was correctly built with HOSTCC and thus failing ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>