package/systemd: explicitly configure split-usr=false and split-bin=true

meson-based build of systemd runs a couple of checks on the structure
of the *host* system which will incorrectly configure systemd if build
host configuration doesn't match Buildroot target.

One can also find the following in the NEWS file:

* A new -Dsplit-bin= build configuration switch may be used to specify
  whether bin and sbin directories are merged, or if they should be
  included separately in $PATH and various listings of executable
  directories. The build configuration scripts will try to autodetect
  the proper values of -Dsplit-usr= and -Dsplit-bin= based on build
  system, but distributions are encouraged to configure this
  explicitly.

Signed-off-by: Alexander Sverdlin <alexander.sverdlin@gmail.com>
Acked-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/systemd/systemd.mk

@@ -29,6 +29,8 @@ SYSTEMD_CONF_OPTS += \
 	-Dldconfig=false \
 	-Ddefault-dnssec=no \
 	-Dtests=false \
+	-Dsplit-bin=true \
+	-Dsplit-usr=false \
 	-Dsystem-uid-max=999 \
 	-Dsystem-gid-max=999 \
 	-Dtelinit-path=$(TARGET_DIR)/sbin/telinit \