overlay.d/05core: Prepare for Ignition migration off sgdisk

Look for sgdisk in the alternative libexec path on EL systems as a
temporary workaround until we complete the migration from gdisk to
fdisk in Ignition.

See: coreos/ignition#1926
See: https://issues.redhat.com/browse/RHEL-56080

overlay.d/05core/usr/lib/dracut/modules.d/35coreos-ignition/coreos-gpt-setup.sh

@@ -26,6 +26,11 @@ if [ "${PTUUID:-}" != "$UNINITIALIZED_GUID" ]; then
     exit 0
 fi
 
+# See: https://github.com/coreos/ignition/issues/1926
+sgdiskcmd="/usr/sbin/sgdisk"
+if [[ -x "/usr/libexec/ignition-sgdisk" ]]; then
+    sgdiskcmd="/usr/libexec/ignition-sgdisk"
+fi
 echo "Randomizing disk GUID"
-sgdisk --disk-guid=R --move-second-header "$PKNAME"
+"$sgdiskcmd" --disk-guid=R --move-second-header "$PKNAME"
 udevadm settle || :