Fallback to /usr/sbin/ldconfig when not in PATH (#532)

[zarmhast]

Summary

• Add fallback to /usr/sbin/ldconfig when ldconfig is not found in $PATH

Description

Some Linux distributions (notably Alpine Linux, Suse) do not include /usr/sbin in the default PATH. This causes lms daemon update to fail on those systems, even though ldconfig is installed and available at /usr/sbin/ldconfig.

This change adds a fallback: if ldconfig is not found via $PATH, the checkLinuxLibatomic() function now also tries /usr/sbin/ldconfig before reporting that ldconfig is unavailable.

Fixes #532.

[github-actions]

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