Change the way SUID bits are managed

Review Request #127341 - Created March 11, 2016 and submitted

Jan Kundrát
The `kcheckpass` binary only needs the SUID bit set when building
without PAM. If PAM is available, then there's no point in having a SUID
bit set in the first place. This is also how, e.g., Gentoo builds this
code anyway.

Also change the way how the SUID bits are managed. Turnes out that cmake
has a feature for this, and I think that using this feature is better
than attempting to call chown & chmod manually.

I don't see a potential for regressions here. The `chown` was previously
attempted as a poor man's UID detection, so if the build was running as
non-root, it wasn't possible to add a proper SUID bit, anyway.

Builds both ways, and the results are as expected. With PAM, everything also works even without the suid bit -- and that's how Gentoo at least has been building this "for ages", AFAIK.

David Edmundson
Jan Kundrát
Review request changed

Status: Closed (submitted)

Change Summary:

Submitted with commit 15057ce538715fa38863b7edab427afe6e92d8f5 by Jan Kundrát to branch master.