P.S. Personally, I think the whole system of W32 Makefiles is in a
dire need of upgrading. It is based on obsolete Makefile.in
prototypes (e.g., DOC is produced by lib-src/makefile, not by
src/makefile), doesn't use some of the latest fixes (e.g., the list of
object files in buildobj.lst is not used), and generally misses some
important dependencies. I don't have the resources to do this, given
that any significant changes will need to be tested on several
versions of Windows and with several sets of development tools.
However, if someone wants to make this happen, I'd suggest to use the
MSDOS method: produce the Windows makefiles from Makefile.in by
editing them with Sed scripts like those in the msdos/ directory. (In
effect, this is modeled after the last part of the Unix configure
script, except that we know the results we should get to.)