CI: add poky-altcfg in xen.yml for systemd image requirement

xen-image-minimal now requires systemd.  Add poky-altcfg (which has
systemd amongst other things) as an includes in the xen.yml file to work
around this.  Also, xen requires openssh instead of dropbear.  So,
override that entry.

Signed-off-by: Jon Mason <jon.mason@arm.com>

.gitlab-ci.yml

@@ -115,16 +115,16 @@ update-repos:
 #
 # Build stage, the actual build jobs
 #
-# Available options for building are
+# Available options for building are (VIRT _must_ be last for ssh override)
 #  DISTRO: [poky, poky-altcfg, poky-tiny]
 #  KERNEL: [linux-yocto, linux-yocto-dev, linux-yocto-rt]
 #  TOOLCHAINS: [gcc, clang, external-gccarm]
 #  TCLIBC: [glibc, musl]
 #  FIRMWARE: [u-boot, edk2]
 #  TS: [none, trusted-services]
-#  VIRT: [none, xen]
 #  TESTING: testimage
 #  SECUREDEBUG: [none, secure-debug]
+#  VIRT: [none, xen]
 
 arm-systemready-ir-acs:
   extends: .build

ci/xen.yml

@@ -4,10 +4,13 @@ header:
   version: 14
   includes:
     - ci/meta-virtualization.yml
+    - ci/poky-altcfg.yml
 
 local_conf_header:
   meta-virt: |
     DISTRO_FEATURES:append = " virtualization xen"
+  sshd: |
+    IMAGE_FEATURES:append = " ssh-server-openssh"
 
 target:
   - xen-image-minimal