Add build switch to separate onscreen and offscreen targets

Add build switch to separate onscreen and offscreen targets

The RPM size of the normal build is about 200MB. This size is due to
packaging of onscreen targets, chrome and content_shell, in the rpm.
This patch separates chrome and content_shell, and other targets
through a build switch.

Command line for onscreen build:
TV: ./tizen_src/build/build_tv.sh --nodebug --build-chrome
Desktop: ./tizen_src/build/build_desktop.sh --build-chrome

Reference:
1. https://review.tizen.org/gerrit/274726/
2. https://review.tizen.org/gerrit/274898/
3. https://review.tizen.org/gerrit/275228/
4. https://review.tizen.org/gerrit/276006/

Change-Id: I77fe89c4a10175b4f1b4ea28f21cba92b5e001f0
Signed-off-by: Ayush Kumar <ayush.k@samsung.com>