Boot method declaration

[Martin Stein]

By now when doing a build there are two ways of defining the boot
method. In 'base-mb' one writes 'RUN_OPT="--target jtag" make demo' or
'RUN_OPT="--target qemu" make demo' while qemu is set by default. At
least in base-hw with imx53 one must enrich the SPECS e.g. in
etc/specs.mk by the 'uboot' spec to get an appropriate Uboot image.

Are there pros or cons for one of these methods, because i would prefer
to use only one them.