Add information about build flags required for metrics
Add information about build flags required for metrics

Signed-off-by: Katarzyna Kujawa <6d81612c80214d850c10c80be3c4dcdb2935414e@intel.com>

linux-on-ibm-z/cadvisor,linux-on-ibm-z/cadvisor,linux-on-ibm-z/cadvisor