livepatch: tests: Make them compile under ARM64

livepatch: tests: Make them compile under ARM64

We need to two things:
1) Wrap the platform-specific objcopy parameters in defines
   The input and output parameters for $(OBJCOPY) are different
   based on the platforms. As such provide them in the
   OBJCOPY_MAGIC define and use that.

2) The alternative is a bit different (exists only under ARM64
   and x86), while and there are no exceptions under ARM at all.
   We use the LIVEPATCH_FEATURE CPU id feature for ARM similar to
   how it is done on x86.

We are not yet attempting to build them under ARM32 so
that is still ifdefed out.

Reviewed-by: Ross Lagerwall <ross.lagerwall@citrix.com>
Acked-by: Julien Grall <julien.grall@arm.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>