```
Fix install-missing-packages when port is missing multiple dependencies
The current implementation of install-missing-packages does not handle
correctly the situation when a port is missing multiple dependencies. pkg(8)
would only get the first missing origin as an argument. All the other origins
would be listed on new lines and would not be passed to pkg(8).
This patch replaces newlines with spaces to avoid this problem. An alternative
solution would be to replace ECHO_CMD with "printf %s" and unquote the _dirs
variable. The implemented solution is cleaner, however, in my opinion (less
magical).
```