systemd: build with -Defi=true on Generic

With kernel 6.0 the legacy efi vars interface at /sys/firmware/efi/vars was removed
(https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit?h=v6.0&id=0f5b2c69a4cbe4166ca24b76d5ada98ed2867741).

The efibootmgr tool requires now to mount the efivarfs pseudo-filesystem on
/sys/firmware/efi/efivars. Enabling upstream EFI support for systemd is the easiest way to
get it mounted on EFI systems but still having correct (non-)support for legacy boot.

No additional files are added to the image.

packages/sysutils/systemd/package.mk

@@ -79,7 +79,6 @@ PKG_MESON_OPTS_TARGET="--libdir=/usr/lib \
                        -Dhwdb=true \
                        -Drfkill=false \
                        -Dldconfig=false \
-                       -Defi=false \
                        -Dtpm=false \
                        -Dima=false \
                        -Dsmack=false \
@@ -102,6 +101,12 @@ PKG_MESON_OPTS_TARGET="--libdir=/usr/lib \
                        -Ddebug-tty=${DEBUG_TTY} \
                        -Dversion-tag=${PKG_VERSION}"
 
+if [ "${PROJECT}" = "Generic" ]; then
+  PKG_MESON_OPTS_TARGET+=" -Defi=true"
+else
+  PKG_MESON_OPTS_TARGET+=" -Defi=false"
+fi
+
 pre_configure_target() {
   export TARGET_CFLAGS="${TARGET_CFLAGS} -fno-schedule-insns -fno-schedule-insns2 -Wno-format-truncation"
   export LC_ALL=en_US.UTF-8