The fonts are now stored in a portable binary format, and are kept in the
data subdirectory.  Just copy them to one of the directories in the plplot
font search path for your system (see the documentation or plfont.c for
more info).

If you really must rebuild the font files, you can do so using the files
in this directory.
[What follows does not apply to the new build sheme]
From the tmp directory, after configuring plplot simply type "make fonts".
This will build the font generating programs, run them, and move the output
font files into the ../lib directory.