Do not show initcpio image file name if it is a temporary file
If a preset doesn't have any `*_image` variables, but only `*_uki`, the initramfs image will generated to a temporary directory before packed in a UKI. This temporary file will be shown in `mkinitcpio` output:
```
==> Creating zstd-compressed initcpio image: '/tmp/mkinitcpio.XpuIsP'
```
There is no use in showing the file name, so it should just be omitted.
issue