Instead of mkextra, take advantage of the /OUT and /IMPLIB command line
flags for MSVC. Namely, format them like this:
/OUT:%s.dll /IMPLIB:%s
where %s is the name of the imports library.
It cannot properly create and link against .DLLs yet, the current
implementation of it is a hack (using mkextra). Static libraries,
executables as well as cc work in a respectable manner.