"shared/nm-meta-setting.[hc]" contains meta data about settings.
As such it is similarly used by libnm-core (as internal API) and
by clients (as extension of public API of libnm). However, it must
be compiled twice, because while it defines in both cases a
NMMetaSettingInfo type, these types are different between internal and
public API.
Hence, the files must also be compiled twice (and differently), once
against libnm-core and once against the client helper library.
Previously, the file was under "shared/", but there it's a bit odd
it doesn't clearly belong anywhere.
There are two goals here:
- copy the file to the two places where it is used. We also have
a "check-tree" unit test that ensures those files don't diverge in
the future.
- we no longer require CFLAGS set during built. Instead, the sources
should control the build. For that we have new (simple) headers
"nm-meta-setting-base.h" that define the right behavior for the
impl files.
There is still an ugliness (among several): the files must be named the
same for libnm-core and clients/common. Preferably, all our sources have
unique names, but that is not possible with this scheme (without
introducing other ugliness). To mitigate that, include the files only at
one exact place.
