The makefiles of the hotspot does not check whether a microsoft tool (like the link.exe) or a cygwin (or MKS) tool is used. There should be added some sanity checks to prevent using the link.exe from cygwin instead of the Microsoft link.exe.
Place the MS VS compiler path before the /bin (or /usr/bin) in the PATH. The order is oppposite to the one required by the J2SE makefiles to work correctly.
Add sanity checks for cl.exe and link.exe on Windows.