wic: build wic-tools only if wic is run manually

wic: build wic-tools only if wic is run manually

When wic can't find native sysroot it tries to build wic-tools
However, it's not possible when wic is run from bitbake.
Moreover, it's not even feasible anymore as wic-tools should be
used only when wic is run manually.

Checked if wic is run manually before building wic-tools.

Signed-off-by: Ed Bartosh <ed.bartosh@linux.intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>