configure: build sulogin, watchdogd, and libsystemd by default

v5.0 ships keventd and the D-Bus support enabled out of the box, but the
remaining bundled pieces stayed opt-in, and the help text for two of them
already claimed otherwise.

Default all three to yes; --without-sulogin, --without-watchdog, and
--without-libsystemd opt out.  The distcheck and CI configure lines drop
the flags they no longer need, so CI exercises the defaults.

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

doc/ChangeLog.md

@@ -69,6 +69,12 @@ All relevant changes are documented in this file.
   `tmpfiles.d/dbus.conf`, so both can be overridden from `/etc` like any other
   system file.  Those directories are no longer chowned to `messagebus`,
   matching how Finit ships directories for other daemons
+- The bundled `sulogin` and `watchdogd`, and the replacement `libsystemd`,
+  are now built and installed by default, like keventd and the D-Bus
+  support.  `--without-sulogin`, `--without-watchdog`, and
+  `--without-libsystemd` opt out.  Note, Finit starts `watchdogd` by
+  itself when the WDT device node exists, and `libsystemd.so` is
+  installed to `$libdir`, where a system with systemd already has one
 - The `tty` block takes `passenv`, which the line-based format has had since
   v4.4 (issue #286) and the block format was missing
 - New `provides` setting for run/task/service/sysv blocks, naming conditions

doc/build.md

@@ -79,9 +79,20 @@ Below are a few of the main switches to configure:
   run mdev, mdevd, or udevd instead.  Enabled by default, and the only
   thing that pulls in libblkid.  See [Bundled Device Manager](keventd.md).
 
-* `--with-sulogin`: Enable bundled `sulogin` program.  Default is to use the
-  system `sulogin(8)`.  The sulogin shipped with Finit *allows password-less*
-  login if the `root` user is disabled or has no password at all.
+* `--without-sulogin`: Drop the bundled `sulogin`, enabled by default,
+  and use the system `sulogin(8)` instead.  The one shipped with Finit
+  *allows password-less* login if the `root` user is disabled or has no
+  password at all.  `--with-sulogin=USER` prompts for another user's
+  password than `root`'s.
+
+* `--without-watchdog`: Drop the bundled `watchdogd`, enabled by default
+  on `/dev/watchdog`, `--with-watchdog=DEV` selects another device.
+  Finit starts it when the device node exists, see [Watchdog](watchdog.md).
+
+* `--without-libsystemd`: Drop the replacement `libsystemd`, built and
+  installed by default, which lets programs that use `sd_notify()` talk
+  to Finit without systemd.  Note, it installs `libsystemd.so` in
+  `$libdir`, where a system with systemd already has one.
 
 For more configure flags, see <kbd>./configure --help</kbd>
 
@@ -108,8 +119,7 @@ Then configure, build and install:
 
 ```shell
 $ ./configure --prefix=/usr                 --exec-prefix=         \
-              --sysconfdir=/etc             --localstatedir=/var   \
-              --with-keventd                --with-watchdog
+              --sysconfdir=/etc             --localstatedir=/var
 $ make
 .
 .

doc/watchdog.md

@@ -1,10 +1,10 @@
 Bundled Watchdog Daemon
 =======================
 
-When built `--with-watchdog` a separate service is built and installed
-in `/libexec/finit/watchdogd`.  If this exists at runtime, and the WDT
-device node exists, Finit will start it and treat it as the elected
-watchdog service to delegate its reboot to.  This delegation is to
+A separate service is built and installed in `/libexec/finit/watchdogd`,
+unless disabled with `--without-watchdog`.  If this exists at runtime,
+and the WDT device node exists, Finit will start it and treat it as the
+elected watchdog service to delegate its reboot to.  This delegation is to
 ensure that the system is rebooted by a hardware watchdog timer -- on
 many embedded systems this is crucial to ensure all circuits on the
 board are properly reset for the next boot, in effect ensuring the