Add a new flag: -I: don't display `quit?' if a package fails.
Also changed that if -I is not used, only display `quit?' if
Display which packages is getting build, useful it more than
one package will be build (though it's broken, see below).
reqs is not empty, meaning it's most likely a dependency.
echo a newline if more than one package is used.
get_deps: no need to check if .deps file exists as that's done
already when it's called.
Add a TODO: reset show_reqs, so that it does not display too many
dependencies for the second, and third ... packages, otherwise they
would have inherited the deps of the first package.