windows: fix build scripts to build googletest and googlemock for windows

[sagarkchitnis]

modify sconscript and related files to build googletest and googlemock for windows

reference changes have been made in : https://github.com/sagarkchitnis/windows
                                     https://github.com/sagarc-contrail/contrail-controller/tree/windows
The above changes are based on 3.1 and similar changes need to be made for mainline (master)

[OpenContrail Admin (ci-admin-f)]

Review in progress for https://review.opencontrail.org/37510
Submitter: sagarkchitnis (<email address hidden>)

[OpenContrail Admin (ci-admin-f)]

Reviewed: https://review.opencontrail.org/37510
Committed: http://github.com/Juniper/contrail-controller/commit/1e9df6850f2009bf50c74125428a0242dd64dc88
Submitter: Zuul (<email address hidden>)
Branch: master

commit 1e9df6850f2009bf50c74125428a0242dd64dc88
Author: U-JNPR\sagarc <email address hidden>
Date: Tue Nov 14 14:05:09 2017 -0800

build gunit/gtest for windows

Original working changes and change history:
https://github.com/sagarkchitnis/windows/commits/master/controller/lib/

subsequent changes in https://github.com/codilime/contrail-controller/tree/windows3.1/lib/

Other minor changes TBD.

Change-Id: I8e884cc00501737cb3cfaa1cff51e26faa7c25bb
Partial-Bug: #1681563