allow for unchanged objects

There are situations in which an object may be rebuilt but have no
functional changes, such as a change to an included header file.

This commit changes kpatch-build to tolerate individual unchanged
objects so long as there is, in the end, at least one changed object.

Signed-off-by: Seth Jennings <sjenning@redhat.com>
Merge pull request #348 from spartacus06/allow-unchanged-object

allow for unchanged objects
kpatch-gcc: split up object exclusion list
kpatch-gcc: exclude system_certificates.o

Fixes the following issue when running kpatch-build against the latest
upstream kernel:

    system_certificates.o: no changed functions were found
kpatch-build: don't link unchanged objects

The FILES variable can contain unchanged objects, so don't use it to
determine which objects to link.  Instead, just use all the objects that
were placed in the output directory by create-diff-object.
Merge pull request #349 from jpoimboe/system_certificates

upstream kernel fixes
support renaming of mangled functions in unbundled sections

Signed-off-by: Seth Jennings <sjenning@redhat.com>