Centralize the definition of the tool name prefix (i.e. "nb") intobsd.own.mk, as the _TOOL_PREFIX variable.
Re-add mktemp as a host tool; it is used in more places than Benthought.
On second thoughts, don't make mktemp a host tool. It's only used once, forcreating a temporary directory for maketars, and mkdir can do that safelyenough.
Add mktemp as a host tool.