[PATCH] expand-on-first-boot: follow symbolic before search slave device

[Quirin Gylstorff <Quirin.Gylstorff@siemens.com>]

From: Quirin Gylstorff <quirin.gylstorff@siemens.com>

The entry in /dev/mapper/... is symbolic link to /dev/dm-<X>.

This solves they following error:
```
Boot device equals root device - no partitioning found
```
in case of the following disk layout
root@demo:~# lsblk
NAME                   MAJ:MIN RM   SIZE RO TYPE  MOUNTPOINTS
sda                      8:0    0   2.5G  0 disk
├─sda1                   8:1    0  47.4M  0 part  /boot
└─sda2                   8:2    0 447.9M  0 part
  └─encrypted_platform 252:0    0 431.9M  0 crypt /

Reported-by: Wang, John <johnxw@amazon.com>
Signed-off-by: Quirin Gylstorff <quirin.gylstorff@siemens.com>
---
 .../expand-on-first-boot/files/expand-last-partition.sh         | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/meta/recipes-support/expand-on-first-boot/files/expand-last-partition.sh b/meta/recipes-support/expand-on-first-boot/files/expand-last-partition.sh
index 0cb2ee21..8770677c 100755
--- a/meta/recipes-support/expand-on-first-boot/files/expand-last-partition.sh
+++ b/meta/recipes-support/expand-on-first-boot/files/expand-last-partition.sh
@@ -9,7 +9,7 @@
 
 set -e
 
-ROOT_DEV="$(findmnt / -o source -n)"
+ROOT_DEV="$(readlink -f "$(findmnt / -o source -n)")"
 ROOT_DEV_NAME=${ROOT_DEV##*/}
 ROOT_DEV_SLAVE=$(find /sys/block/"${ROOT_DEV_NAME}"/slaves -mindepth 1 -print -quit 2>/dev/null || true)
 while [ -d "${ROOT_DEV_SLAVE}/slaves" ]; do
-- 
2.43.0