systemd: fix path for kmod in service files

The path for kmod used in kmod-static-nodes.service is the one found by
the ./configure script, which ends up being the path to the host kmod
program.

This patch forces the path to the target kmod program.

Signed-off-by: Eric Le Bihan <eric.le.bihan.dev@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/systemd/systemd.mk

@@ -50,6 +50,10 @@ SYSTEMD_CONF_OPT += \
 	--disable-dbus \
 	--without-python
 
+# Override path to kmod, used in kmod-static-nodes.service
+SYSTEMD_CONF_ENV = \
+	ac_cv_path_KMOD=/usr/bin/kmod
+
 ifeq ($(BR2_PACKAGE_SYSTEMD_COMPAT),y)
 SYSTEMD_CONF_OPT += --enable-compat-libs
 else