logging: Add option to not generate dictionary database always

Add option to not generate the logging dictionary database when the
zephyr finale image is created. Instead this database can be created
by its own build target.
This reduces the build time during debugging as the database file is not
required as part of the debugging.

Fix build byproducts not listing the output file.
Add comment so users know which command is executing as this command
can take a long time.

Signed-off-by: Joakim Andersson <joakim.andersson@heimdallpower.com>