I usually set some COPTS.  I can build distribution sets this way, but build release
fails because of exceeding size of floppy images or something like that:

#    create  ramdisk-small/ramdisk-small.fs
nbmakefs: `work' size of 2031616 is larger than the maxsize of 1744896.

*** Failed target:  ramdisk-small.fs

And I wonder if C options used for creating those images can be separated from COPTS somehow?