os-release is available on FreeBSD by default.
Also avoid executing a third-party program.
Examples:
Linux 5.10.0-3-amd64 [x86_64] @ Debian GNU/Linux bullseye/sid
FreeBSD 12.2-RELEASE-p3 [amd64]
Closes: #516
Unavailable values are returned as "n/a" from lsb_release, skip these.
$ lsb_release -a
LSB Version: 1.4
Distributor ID: Arch
Description: Arch Linux
Release: rolling
Codename: n/a
At start, SysArchMeter calls the uname function to obtain the kernel
version and architecture. If available, the distro version is obtained
by calling lsb_release. The obtained values are stored in static
variables and used when updating the meter.
Benny Baumann