To cross compile for Windows, the following needs to be done:

1) Uncomment the lines under "mingw" in config.mk, and comment any earlier CC & LDFLAGS lines.

2) Compile a copy of openssl for mingw.
   Download OpenSSL from openssl.org, then run:
  ./Configure mingw --cross-compile-prefix=i686-w64-mingw32-
  make 

3) Set the OPENSSLDIR variable in config.mk to match where you compiled openssl

4: Set up tcl Starkit prerequisites:
   Download tclkit from http://tclkits.rkeene.org/fossil/wiki/Downloads
   Download sdx from https://chiselapp.com/user/aspect/repository/sdx/index
   Create a shell script called sdx and put it in your path, containing something like this:
  #!/bin/sh
  d="$HOME/src/getxbook"
  "$d/tclkit-8.6.3-rhel5-x86_64" "$d/sdx-20110317.kit" "$@"
  Download a windows tclkit including tk from http://tclkits.rkeene.org/fossil/wiki/Downloads and ensure the adjust W32TCLKIT to the appropriate filename in config.mk if needed

Then 'make' and 'make dist-win' should all work as expected