librt: Chase 315ee00fa961, fixing boot

[cy]

Summary

libzfs uses librt as a dependency. Following 315ee00fa961 systems with
a separate / and /usr will fail to load the libzfs.so library because
librt.so is not available due to the fact that /usr is not mounted yet.
Install librt in /lib making it available to libzfs.

Fixes: 315ee00fa961

Test Plan

Works locally

[imp]

Need obsolete files entry or a sym link from the old place???

[emaste]

Yes, MOVED_LIBS entry in ObsoleteFiles.inc

[cy]

In D41612#948300, @emaste wrote:

Yes, MOVED_LIBS entry in ObsoleteFiles.inc

Added.

[cy]

Added MOVED_LIBS+=usr/lib/librt.so.1.

[emaste]

ObsoleteFiles.inc

54

should have a short description, e.g. 20230828: librt moved to /lib

[mm]

Looks like jrtc27@ has already committed the lib/librt/Makefile part

[mm]

But thanks I have to track this because the same will happen for the merge from zfs-2.2-release to stable/14

[emaste]

But thanks I have to track this because the same will happen for the merge from zfs-2.2-release to stable/14

We should just merge all of the librt changes to stable/14 (as one commit) likely in 3 days, in advance of the ZFS merge.