livepatch/klp-build: Add --show-first-changed option to show function divergence

livepatch/klp-build: Add --show-first-changed option to show function divergence

Add a --show-first-changed option to identify where changed functions
begin to diverge:

  - Parse 'objtool klp diff' output to find changed functions.

  - Run objtool again on each object with --debug-checksum=<funcs>.

  - Diff the per-instruction checksum debug output to locate the first
    differing instruction.

This can be useful for quickly determining where and why a function
changed.

Acked-by: Petr Mladek <pmladek@suse.com>
Tested-by: Joe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>