[MLton] mlnlffigen is awesome (was: bootstrap problem)

[Matthew Fluet]

> I would probably argue (although weakly) for having MLB path variables in
> a file instead of the command line (with the command line arg just pointing
> to the file).  The argument is that often different projects can share
> the variables so the extra indirection is useful.

Other reasons for only putting them in a file:
 * paths to libraries tend to be long (albeit, from the shell you might 
   have path completion)
 * defining a path in term of other path variables may require extra 
   quoting to protect an MLB path variable from shell/environment variable
   expansion