[packages] Fix incorrect OS value set in Mimir v2.3.* RPM package

[wilfriedroset]

What this PR does

When creating the packages on MacOS the OS applied on the package is not correct. The documentation says:

--rpm-os OS
The operating system to target this rpm for. You want to set this to ‘linux’ if you are using fpm on OS X, for example

See: https://fpm.readthedocs.io/en/latest/packages/rpm.html

Which issue(s) this PR fixes or relates to

Fixes #3216

Checklist

• Tests updated
• Documentation added
• CHANGELOG.md updated - the order of entries should be [CHANGE], [FEATURE], [ENHANCEMENT], [BUGFIX]

[wilfriedroset]

Here is the resulting package build with this patch mimir.zip

[root@wr ~]# cat /etc/redhat-release
Rocky Linux release 8.6 (Green Obsidian)
[root@wr ~]# rpm -qp --qf '%{OS}\n' mimir-*.rpm
linux
[root@wr ~]# yum install mimir-2.3.1_amd64.rpm
Last metadata expiration check: 0:45:28 ago on Fri 14 Oct 2022 04:22:38 PM UTC.
Dependencies resolved.
==============================================================================================================================================================
 Package                            Architecture                        Version                               Repository                                 Size
==============================================================================================================================================================
Installing:
 mimir                              x86_64                              2.3.1-1                               @commandline                               17 M

Transaction Summary
==============================================================================================================================================================
Install  1 Package

Total size: 17 M
Installed size: 50 M
Is this ok [y/N]: y
Downloading Packages:
Running transaction check
Transaction check succeeded.
Running transaction test
Transaction test succeeded.
Running transaction
  Preparing        :                                                                                                                                      1/1
  Installing       : mimir-2.3.1-1.x86_64                                                                                                                 1/1
  Running scriptlet: mimir-2.3.1-1.x86_64                                                                                                                 1/1
  Verifying        : mimir-2.3.1-1.x86_64                                                                                                                 1/1

Installed:
  mimir-2.3.1-1.x86_64

Complete!

[treid314]

Thank you!

[grafanabot]

The backport to release-2.4 failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new branch
git switch --create backport-3221-to-release-2.4 origin/release-2.4
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x 80e6fc10e7328fc38e156327be48b11d0c1f02e2
# Push it to GitHub
git push --set-upstream origin backport-3221-to-release-2.4
git switch main
# Remove the local backport branch
git branch -D backport-3221-to-release-2.4

Then, create a pull request where the base branch is release-2.4 and the compare/head branch is backport-3221-to-release-2.4.