images: Introduce sysmocom-voice-sip-image.bb

This image contains a CS-only NITB with osmo-sip-connector.

Related: SYS#5326

recipes-apps/images/sysmocom-voice-sip-image.bb

@@ -0,0 +1,11 @@
+require sysmocom-image.inc
+
+IMAGE_INSTALL_append = " task-sysmocom-cs osmo-sip-connector "
+
+# osmo-pcu is included in sysmobts targets due to machine .conf depending on
+# task-sysmocom-bts. Since we only want voice here, let's disable osmo-pcu and
+# be done with it:
+disable_systemd_osmo_pcu() {
+        rm -f ${IMAGE_ROOTFS}/etc/systemd/system/multi-user.target.wants/osmo-pcu.service
+}
+IMAGE_PREPROCESS_COMMAND += "disable_systemd_osmo_pcu "