It seems some target started declaring package in DEVICE_PACKAGES just
to call InstallDev and generate binary for the image firmware.
This is very much used by layerscape target where trusted-firmware-a and
dependency are called for final image generation.
This is problematic for APK since it's more sensible to non exisiting
package.
To handle this, introduce a prefix '~' for a package that will signal to
build the package but not install it in the final image.
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
