[FS#86] Can't generate Solidrun Clearfog A1 Pro image

[LEDE Bugs]

The following task has a new comment added:

FS#86 - Can't generate Solidrun Clearfog A1 Pro image
User who did this - Artox (Artox)

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I have been working on this for the past days, with a setback when teh switch to new image building code happened.
However my goal was: a bootable image for sdcard, that is compelte with partition table, boot script and rootfs.

Let me quickly share the current state (Just now I managed to build an actually working sdcard image):
4GB sdcard (actually the numbers are wrong, I need to fix them because its bigger than an sdcard sold as 4GB)
MBR: 3 partitions boot | rootfs(squashfs) | rootfs_data(ext4)
Please find the current patch attached. It is not ready for submission yet!
I still intend to fix those numbers, and make the sdcard size configurable.

But please comment if you have any thoughts here.

Open Questions:
Where does the bootloader image end up (that u-boot.mmc I am using comes from the SolidRun fork)?
Can it be automatically selected as a build dependency?
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One or more files have been attached.

More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=86#comment209