IOT-1749: Enabling multi-threaded builds in Windows.

IOT-1749: Enabling multi-threaded builds in Windows.

I've modified the global env configuration and run.bat in order
to make parallel builds possible and generate private symbols files
at the same time.

Change-Id: I770b5a57e4fb8b437b727d7937f37a411e2f6cca
Signed-off-by: Pawel Winogrodzki <pawelwi@microsoft.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/16553
Tested-by: jenkins-iotivity <jenkins@iotivity.org>
Reviewed-by: Dan Mihai <Daniel.Mihai@microsoft.com>