n1sdp: Introduce bash based build scripts

This patch introduces bash based build scripts to build n1sdp
software components.

- Each component has a separate build-[COMPONENT].sh bash shell script.
- The script prepares disk images for BusyBox and Ubuntu filesystems
  with GRUB configurations.

Change-Id: I6949cba125533233b6694e085e4312bc2e9e2807
Signed-off-by: Khasim Syed Mohammed <khasim.mohammed@arm.com>