Fix build issues due to updated arm-sdk

Due to recent changes made in arm-sdk,
the FORTIFY_SOURCE security flag enables optimization level 2.

The repo has a default debug level of optimization which conflicts with
FORTIFY_SOURCE flag.

In this commit the default build type is set to debugoptimized and also made sure
to disable the FORTIFY_SOURCE when we need to build without any optimization.

Signed-off-by: PriyangaRamasamy <priyanga24@in.ibm.com>
Change-Id: I73c3dea7e4860dc606e26cd0f6cd31e60ff8105d