[Bug]: armbian-install fails on a Raxda q6a with emmc

### What happened?

When I try to install the armbian system from the SDcard onto the emmc, it keeps failing and the system doesn't boot from the emmc.

### How to reproduce?

Use a Raxda Q6A, install armbian on a SDcard and this all works fine.
The install a smallish emmc card (16GB in my case) and try to install the system onto the emmc. It seems to complete but then the system never boot from emmc.

### Branch

main (main development branch)

### On which host OS are you running the build script and observing this problem?

Debian 13 Trixie

### Are you building on Windows WSL2?

- [ ] Yes, my Ubuntu/Debian/OtherOS is running on WSL2

### Relevant log URL

_No response_

### Code of Conduct

- [x] I agree to follow this project's Code of Conduct

Start by reproducing the armbian-install flow on a Raxda Q6A with a 16GB eMMC, using the working SD-card installation as a comparison. Inspect the installation output and resulting eMMC boot artifacts; done means the install completes without errors and the board boots from eMMC after the SD card is removed.

Written by the indexing model from the issue text.