conf/layer.conf: Use BBFILES_DYNAMIC to handle dynamic-layers
conf/layer.conf: Use BBFILES_DYNAMIC to handle dynamic-layers

BBFILES_DYNAMIC can be used to activate content only when given
layers are present.

For now just add qt5 layer to the BBFILES_DYNAMIC list

Signed-off-by: Khem Raj <729d64b6f67515e258459a5f6d20ec88b2caf8df@gmail.com>

agherzan/meta-raspberrypi,leon-anavi/meta-raspberrypi,agherzan/meta-raspberrypi,schnitzeltony/meta-raspberrypi,schnitzeltony/meta-raspberrypi,agherzan/meta-raspberrypi,leon-anavi/meta-raspberrypi,leon-anavi/meta-raspberrypi,agherzan/meta-raspberrypi,agherzan/meta-raspberrypi,schnitzeltony/meta-raspberrypi,agherzan/meta-raspberrypi