two cons portability niggles

[David Sanderson]

I have encountered a few oddities when trying to use cons on both
Windows and Unix.

1) It would be nice if the reference-to-a-list-of-directories idiom were
carried to the ENV parameter as well.  That is, if the value of an ENV
key was a reference to a list, cons would do a

        join($PATH_SEPARATOR, ...)

on that list for you as it constructed the environment for executing a
child process.  That rule would let you specify not only PATH, but also
other directory lists, without having to worry about the path separator
explicitly.

2) It struck me as nonintuitive that in order to write a portable Library
rule, I had to use PREFLIB explicitly.  For instance:

    Library $CONS "$LIB/%{PREFLIB}foo", @foo_sources;

Cons infers SUFLIB automatically if it is not already there, so it
seemed odd to me that it did not supply PREFLIB automatically if it was
not already there.  I am not sure if there would be any deep issues of
compatibility with existing systems in making this change, but I thought
I'd point it out.

David Sanderson (address@hidden)