sgi/build-test-ras: add build support for validating ras functionality

Add support for building the sgi platform software stack for validating
the RAS error injection and error handling capabilities. Except for grub,
all the other components gets built as part of the build process.

The build requires a prebuilt fedora disk image. The compiled linux kernel
is loaded into this prebuilt disk image during the package stage.

Change-Id: I93c99ef06b315a2cbfdb42d5fc7b5c0e269379a4
Signed-off-by: Sughosh Ganu <sughosh.ganu@arm.com>