Those variables will be sanitized by bsd.own.mk. Same are renamed and others are checked (integrity, consistency, conflicttion, dependency, ...). For example MKSOFTFLOAT will be converted to USE_SOFTFLOAT or __USE_SOFTFLOAT or NETBSD_CONFIG_USE_SOFTFLOAT or whatever namespace and used in the tree. MKSOFTFLOAT stands as user interface. I would be happy to see any bugs in MK* and USE* fixed. But I do not understand what the problem is and why mass renaming is helpful. The MK* and USE* notion seems entirely sensible, and the only thing that is perhaps wrong is that the docs aren't good enough.
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