contrib/rpm: use meson by default for builds on rawhide
Summary
This MR makes it so that meson is used by default to build the specfile on Rawhide (Fedora >40).
Purpose
As part of our plan to deprecate autotools, we will now be using meson by default to build NM releases on Rawhide.
Checklist
Please read https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/blob/main/CONTRIBUTING.md before opening the merge request. In particular, check that:
-
the subject for all commits is concise and explicative -
the message for all commits explains the reason for the change -
the source is properly formatted -
any relevant documentation is up to date -
you have added unit tests if applicable -
the NEWS file is updated when the change deserves to be mentioned, for example for new features, behavior changes, API deprecations, etc.