Since "src" is a fetchsvn directory, the source is copied with "cp
--no-preserve=timestamps" (see commit
6d928ab684). So some source files might
get a slightly different timestamp. Here, if lib/standard.ppmdfont
gets a newer timestamp than the generated file lib/standardppmdfont.c,
Make will try to rebuild the latter. But that fails because the
ppmdcfont program doesn't exist (yet).
Probably stdenv should ensure that every file has the same timestamp.
4dd9507b83