extlibs: Removing redundant configuration
extlibs: Removing redundant configuration

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

Bug: https://jira.iotivity.org/browse/IOT-1583
Change-Id: Iacd5905d3c221d3d1a142f08a5ea61a899ad08b1
Signed-off-by: Pawel Winogrodzki <86015b4aa5c210d1e1d093865be7781a2e47e04a@microsoft.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/21299
Tested-by: jenkins-iotivity <d95b56ce41a2e1ac4cecdd398defd7414407cc08@iotivity.org>
Reviewed-by: Phil Coval <ff46fec9739d31cce915aabcc3a7a2c00eee4d6c@osg.samsung.com>
(cherry picked from commit 038ec8e2d700d06722c9db43b41b8c534deb42ce)
Reviewed-on: https://gerrit.iotivity.org/gerrit/21441
Reviewed-by: George Nash <acbdc39d528a4315fe0b532d55c50ae46f5c1667@intel.com>
Reviewed-by: Rick Bell <74cf0087f675c7c2d5c6f65986a0832071d4b512@intel.com>
Reviewed-by: Mats Wichmann <7a5e6f27299d2bbd9d04b59d9e8e4f8eab83d8cb@linux.com>

rzr/iotivity,iotivity/iotivity,rzr/iotivity,rzr/iotivity,iotivity/iotivity,rzr/iotivity,iotivity/iotivity,iotivity/iotivity,rzr/iotivity,rzr/iotivity,iotivity/iotivity,rzr/iotivity,iotivity/iotivity,iotivity/iotivity,iotivity/iotivity