The mingw/mingw-msys makefiles should be ok, as this problem isn't related to the makefiles. Basically, extras.scm contains references to random/srandom that shouldn't be there -- and this has already been rectified in r15559 (http://www.irp.oist.jp/trac/chicken/changeset/15559), these fixes aren't reflected in the 4.2.0 tarball though, for some strange reason.