tools power x86_energy_perf_policy: Override CFLAGS assignments and add LDFLAGS to build command

So user could specify outside CFLAGS/LDFLAGS values.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Herton Krzesinski <herton@redhat.com>
Cc: Len Brown <len.brown@intel.com>
Link: https://lkml.kernel.org/r/20181212102537.25902-2-jolsa@kernel.org


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