Bug#910727: Overlays cannot be applied to dtbs - missing DTC_FLAGS='-@'

[Nicolas Frattaroli <frattaroli.nicolas@gmail.com>]

Hello,

I realise this is quite an old bug, but it would still be of interest
to me to get this enabled. The -@ option will increase the size of the
compiled device tree blobs somewhat, but on the flipside, u-boot-menu's
device tree overlay functionality will actually be useful.

In my case, I'm interested in this for PINE64's Quartz64 lineup of ARM
devices. Since these are development boards that expose non-enumerating
protocols like I2C and SPI, the use of device tree overlays is pretty
much required to add additional modules to the board.

Kind regards,
Nicolas Frattaroli