meson: make "developer" mode the default

This means that the dbus doc consistency checks will be enabled by default,
including in the CI. I think that will work better than current state where
people do not enable them and them follow-up patches for the docs like the
parent commit must be had.

docs/HACKING.md

@@ -99,6 +99,13 @@ And after that, head over to your repo on GitHub and click "Compare & pull reque
 Happy hacking!
 
 
+## Developer and release modes
+
+In the default meson configuration (`-Dmode=developer`), certain checks are
+enabled that are suitable when hacking on systemd (such as internal
+documentation consistency checks). Those are not useful when compiling for code
+for distribution and can be disabled by setting `-Dmode=release`.
+
 ## Fuzzers
 
 systemd includes fuzzers in `src/fuzz/` that use libFuzzer and are automatically

meson.build

@@ -3503,6 +3503,7 @@ watchdog_opt = service_watchdog == '' ? 'disabled' : service_watchdog
 status = [
         '@0@ @1@'.format(meson.project_name(), meson.project_version()),
 
+        'build mode:                        @0@'.format(get_option('mode')),
         'split /usr:                        @0@'.format(split_usr),
         'split bin-sbin:                    @0@'.format(split_bin),
         'prefix directory:                  @0@'.format(prefixdir),

meson_options.txt

@@ -4,7 +4,7 @@
 option('version-tag', type : 'string',
        description : 'override the git version string')
 
-option('mode', type : 'combo', choices : ['default', 'developer'],
+option('mode', type : 'combo', choices : ['developer', 'release'],
        description : 'enable additional checks suitable for systemd development')
 
 option('split-usr', type : 'combo', choices : ['auto', 'true', 'false'],