fixup! Fixed return status for tv and mobile build scripts.

fixup! Fixed return status for tv and mobile build scripts.

Previoulsy the build script build/build_mobile|tv.sh always returned 1.
This is because
- if GBS_RET is 0, [ "$GBS_RET" != "0" ] is evaluated to 1,
  which in turn becomes the return value of the script.
- if GBS_RET is 1, the script exits with the value of GBS_RET.

The solution is to exit with 0 at the end of script.
Reviewed by:  Antonio Gomes, mohan reddy, Kangil Han

Change-Id: I1647dfb3d63ca9b60ac2a7b77421540ef7108175
Signed-off-by: SeungSeop Park <sns.park@samsung.com>