Move the s390 arch objects building under build framework to be included
in the libperf build object.

Signed-off-by: Jiri Olsa
Tested-by: Sukadev Bhattiprolu
Tested-by: Will Deacon
Cc: Alexis Berlemont
Cc: Borislav Petkov
Cc: Corey Ashford
Cc: David Ahern
Cc: Frederic Weisbecker
Cc: Namhyung Kim
Cc: Paul Mackerras
Cc: Peter Zijlstra
Cc: Stephane Eranian
Link: http://lkml.kernel.org/n/tip-8f5tlfwegkirhir2ffz8nw3i@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo