bridging: Cleaning up SConscript files.

bridging: Cleaning up SConscript files.

Removing settings already present in the global "env" variable
along with any modifications to that global environment to get rid
of cross dependencies between scripts and forcing them to be executed
in a specific order.

Bug: https://jira.iotivity.org/browse/IOT-1583
Change-Id: I383e01dcfaf23a323d51199e5d091e57751659bc
Signed-off-by: Pawel Winogrodzki <pawelwi@microsoft.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/20943
Tested-by: jenkins-iotivity <jenkins@iotivity.org>
Reviewed-by: Dan Mihai <Daniel.Mihai@microsoft.com>
Reviewed-by: Phil Coval <philippe.coval@osg.samsung.com>