elfcompress: Don't rewrite file if no section data needs to be updated.

elfcompress: Don't rewrite file if no section data needs to be updated.

If the input and output file are the same and no section needs to
be updated we really don't need to rewrite the file.

Check whether any matching section is already compressed or decompressed.
Skip the section if it doesn't need to be changed. If no section data
needs updating end with success without rewriting/updating file.

With --force the file will still always be updated/rewritten even if
no section data needs to be (de)compressed.

Acked-by: Igor Gnatenko <ignatenkobrain@fedoraproject.org>
Signed-off-by: Mark Wielaard <mark@klomp.org>