Draft: Add dummy device family to help port Mobian to new devices

Porting a new device to Mobian often involves adding custom config files and packages, requiring heavy modifications to the existing recipes.

By providing a dummy device family and a few changes to the build script, we can provide an infrastructure for such custom changes:

• .deb packages put in devices/wip/packages will be automatically installed (along with their dependencies)
• device-dependent firmware files should be copied to devices/wip/firmware so they're automatically deployed to /lib/firmware on the device's rootfs
• the directory structure under devices/wip/rootfs will be copied to the image's / (overwriting existing files if needed)

Building such a custom image can be done by executing the following command:

./build.sh -i -t wip-<arch>:<vendor>+<device>

Where:

• is the processor architecture (one of amd64, armhf or arm64)
• is the processor manufacturer as it appears in the kernel's arch/<arch>/boot/dts/ folder (qcom for Qualcomm, allwinner for Allwinner, freescale for NXP...)
• is the DTS filename corresponding to the device (ex: sdm845-oneplus-enchilada for the OnePlus6)

Note: for armhf devices, DTB files are all put under arch/arm/boot/dts and there is no per-vendor subfolder. In that case, the target name would be wip-<arch>:+<device> (ex: wip-armhf:+qcom-msm8974-lge-nexus5-hammerhead for the Google/LG Nexus 5)

It is recommended to append the following additional flags:

• -r for Android devices
• -m 4G if you experience build failures
• -F ext4 if your kernel has F2FS support compiled as a module (please note ext4 support must be built-in)

This should hopefully help porting Mobian to more devices.