CMakeLists: add MOJ_DEBUG flag for DEBUG build

:Release Notes:

:Detailed Notes:

:Testing Performed:
Testing on local environment

:QA Notes:

:Issues Addressed:
[GF-8339] Support external media in ActivityManager

Open-webOS-DCO-1.0-Signed-off-by: Maksym Sditanov <msditanov@luxoft.com>

Change-Id: I9196266ea4fea0d08a10a3b29d4ec01a6b5d80d3
Reviewed-on: https://g2g.palm.com/2954
Reviewed-by: Build Verification
Reviewed-by: Maksym Sditanov <msditanov@luxoft.com>
Tested-by: Maksym Sditanov <msditanov@luxoft.com>
Reviewed-by: Roger Stringer <roger.stringer@lge.com>