livepatch/klp-build: fix shellcheck complaints

livepatch/klp-build: fix shellcheck complaints

Fix or suppress the following shellcheck warnings:

  In klp-build line 57:
  	command grep "$@" || true
                               ^--^ SC2317 (info): Command appears to be unreachable. Check usage (or ignore if invoked indirectly).

Fix the following warning:

  In klp-build line 565:
  		local file_dir="$(dirname "$file")"
                        ^------^ SC2034 (warning): file_dir appears unused. Verify use (or export if used externally).

Acked-by: Song Liu <song@kernel.org>
Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com>
Link: https://patch.msgid.link/20260310203751.1479229-8-joe.lawrence@redhat.com
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>