Required read-only-root-fs for SL-Micro test build

Changes from the SL-Micro team requires adaptions to the
integration test description

Author: schaefi

build-tests/x86/tumbleweed/test-image-MicroOS/appliance.kiwi

@@ -126,6 +126,7 @@
         <package name="squashfs"/>
         <package name="systemd-network"/>
         <package name="systemd-resolved"/>
+        <package name="read-only-root-fs"/>
         <package name="NetworkManager"/>
     </packages>
     <packages type="bootstrap">

build-tests/x86/tumbleweed/test-image-MicroOS/root/etc/fstab.script

@@ -0,0 +1,9 @@
+#!/bin/sh
+set -eux
+
+/usr/sbin/setup-fstab-for-overlayfs
+# If /var is on a different partition than /...
+if [ "$(findmnt -snT / -o SOURCE)" != "$(findmnt -snT /var -o SOURCE)" ]; then
+    # ... set options for autoexpanding /var
+    gawk -i inplace '$2 == "/var" { $4 = $4",x-growpart.grow,x-systemd.growfs" } { print $0 }' /etc/fstab
+fi