linux64: Fix the build on arm64 with bti checking

[andrew]

Summary

When we enable checking for BTI on arm64 we need to include an ELF
not in all object files linked into a module.

As using objcopy from a binary to an ELF object file doesn't add the
note switch to using .incbin from an assembly file. This allows us to
add the needed note without affecting the included object.

Sponsored by: Arm Ltd

[emaste]

Getting rid of ${OBJCOPY_TARGET} is a nice side effect

[imp]

I rather like this for some reason.

[kib]

s/not/note/ in the commit message