examples: Removing redundant configuration

examples: Removing redundant configuration

Moving global environment configuration common for all
platforms into build_common/SConscript and removing repeated
lines from service/examples/*.

Bug: https://jira.iotivity.org/browse/IOT-1583
Change-Id: Icc1661f2e54c27efbaa9787d082a0e2e121e0e20
Signed-off-by: Pawel Winogrodzki <pawelwi@microsoft.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/21477
Reviewed-by: Phil Coval <philippe.coval@osg.samsung.com>
Tested-by: jenkins-iotivity <jenkins@iotivity.org>
Reviewed-by: George Nash <george.nash@intel.com>
Reviewed-by: Dan Mihai <Daniel.Mihai@microsoft.com>