Fix logging of stderr data in command calls

[schaefi]

The stderr data was presented as one blob without line breaks. Hard to read and smells like a bug. This commit fixes the output to become readable

[Conan-Kudo]

Do we have sample output to indicate this is fixed?

[schaefi]

yes in any of the integration test images which uses set -x the shell debug data is placed to stderr. I will update kiwi in Staging, so you can check yourself

[schaefi]

For example

[  208s] [ INFO    ]: 15:22:38 | Calling config.sh script
[  208s] [ DEBUG   ]: 15:22:38 | --------------out start-------------
[  208s] [ DEBUG   ]: 15:22:38 | Configure image: [kiwi-test-image-overlayroot]...
[  208s] [ DEBUG   ]: 15:22:38 | --------------out stop--------------
[  208s] [ DEBUG   ]: 15:22:38 | --------------err start-------------
[  208s] [ DEBUG   ]: 15:22:38 | + declare kiwi_iname=kiwi-test-image-overlayroot
[  208s] [ DEBUG   ]: 15:22:38 | + declare kiwi_profiles=sdboot_erofs
[  208s] [ DEBUG   ]: 15:22:38 | + echo 'Configure image: [kiwi-test-image-overlayroot]...'
[  208s] [ DEBUG   ]: 15:22:38 | + systemctl enable sshd
[  208s] [ DEBUG   ]: 15:22:38 | Created symlink '/etc/systemd/system/multi-user.target.wants/sshd.service' → '/usr/lib/systemd/system/sshd.service'.
[  208s] [ DEBUG   ]: 15:22:38 | + mkdir -p /efi
[  208s] [ DEBUG   ]: 15:22:38 | + for profile in ${kiwi_profiles//,/ }
[  208s] [ DEBUG   ]: 15:22:38 | + '[' sdboot_erofs = grub_verity_erofs ']'
[  208s] [ DEBUG   ]: 15:22:38 | + '[' sdboot_erofs = sdboot_uki_verity_erofs ']'
[  208s] [ DEBUG   ]: 15:22:38 | + rm -f /usr/lib/modprobe.d/60-blacklist_fs-erofs.conf
[  208s] [ DEBUG   ]: 15:22:38 | 
[  208s] [ DEBUG   ]: 15:22:38 | --------------err stop--------------

from

https://build.opensuse.org/package/live_build_log/Virtualization:Appliances:Images:Testing_x86:tumbleweed/test-image-overlayroot:sdboot_erofs/images/x86_64