HWC screencap portability improvement

Summary: Removing the only reference to the hardcoded full unix path of screencap.
This will help with portability.

Test: Successful Build on master branch

Change-Id: I8cb83cf312c5dea6f2688864b84145d8eb47be3d
Signed-off-by: Abdelrahman Daim <adaim@meta.com>