linux64: Fix the build on arm64 with bti checking

When we enable checking for BTI on arm64 we need to include an ELF
note 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.

Reviewed by: imp, kib, emaste
Sponsored by: Arm Ltd
Differential Revision: https://reviews.freebsd.org/D45468

(cherry picked from commit bed65d85c631c3a8e60a81a15a5a745c8ef92fbe)
(cherry picked from commit ec69d230933f82c7c142b053882255aa57475463)