Install Linux binaries in /opt instead of /usr/local to support Fedora Silverblue

[strugee]

On Fedora Silverblue, a immutable, atomic desktop, /usr/local is a mutable area of the filesystem reserved for the local system administrator. Therefore, it is not present during package installation, resulting in a "No such file or directory" error when installing Kolide's RPMs.

Instead, Kolide should drop binaries in /opt. See hier(7).

See also #896 (comment)

[strugee]

FYI, I don't have the full command in front of me at the moment but I got this completely working last night by passing -bin_root_dir /opt to package-builder (though I hit some confusing bugginess around argument ordering for a long while).

So this should be trivial to fix. (/var/lib/kolide-k2 or whatever it was in the RPM package won't get created properly on ostree systems, including Silverblue, but this appears to not be a problem since the daemon apparently recreates this directory if it's missing. And RPM packages creating /var directories is evil anyway.)