gtest: Add recipe for v1.6.0

:Release Notes:
Google gtest is needed for building and running unit tests.

:Detailed Notes:

:Testing Performed:
Checked the sysroot is populated with needed files.

:QA Notes:

:Issues Addressed:
[GF-3384] Create an OE component for GTest
[GF-11845] CCC: gtest=1.6.0

Open-webOS-DCO-1.0-Signed-off-by: Heegoo Han <heegoo.han@lge.com>
Open-webOS-DCO-1.0-Signed-off-by: Anatolii Sakhnik <anatolii.sakhnik@lge.com>

Change-Id: I12f5bab3895b588e7640a28b41827c7521d98187
Reviewed-on: https://g2g.palm.com/2550
Reviewed-by: Anatolii Sakhnik <anatolii.sakhnik@lge.com>
Tested-by: Anatolii Sakhnik <anatolii.sakhnik@lge.com>
Reviewed-by: Build Verification
Reviewed-by: Keith Derrick <keith.derrick@lge.com>
Reviewed-by: Susan Montooth <susan.montooth@lge.com>