The two intended uses cases for the _pkg_extra_* macros were to
make it easier for packagers to add new compile flags for use
with their package and also to make it easier to do distro wide
experiments with new flags.
However, it was pointed out on the mailing list[1] that you
can't satisfy both of these uses cases at the same time with
just one set of macros. For example, if a packager uses
_pkg_extra_* macros to add flags specific to their own
package, then someone using _pkg_extra_* macros to
apply a new flag distro wide would override the package
specific flag.
I feel like the distro-wide use case is much more important,
so rather than create two sets of new flags, one for each use
case, I think it's best to rename the _pkg_extra_* macros
to _distro_extra_* and document that they are only meant
to be used for adding distro-wide flags and packagers should
not use this macro.
[1] https://lists.fedoraproject.org/archives/list/devel@lists.fedoraproject.org/message/TOG5RHWPS3VYMM52HFGZOUJVRCGZ7VXB/
Tom Stellard