Ah! There shouldn't be a '.' in "./bin/nasm", of course (unless you're running make install from "/"... which might be the easiest way to fix it). I'm not sure where that's coming from, but for now, just hand-edit it out of the Makefile... "prefix"->"exec_prefix"->"bindir" sets up where install tries to put it... (FWIW, my machine puts nasm in /usr/local/bin - I'd think that, or /usr/bin would make more sense than /bin)
When you get to building 0.98.39 - which you really should do, unless you like buffer overruns - you'll need to edit Makefile and rdoff/Makefile to delete the references to "std=c99", I think.
Best,
Frank