Add the mkisofs package to the Windows mkbuildmachine scripts.

This adds the genisoimage command. Also update the cygwin installer
checksum as there is a new one.

OXT-65

Signed-off-by: Ross Philipson <ross.philipson@gmail.com>
Add support for generating a Windows only tools ISO

This will not break existing build machines that do not have
the genisoimage for cygwing. Once aded the stage step will start
creating the ISO.

OXT-65

Singed-off-by: Ross Philipson <ross.philipson@gmail.com>
Merge pull request #43 from rossphilipson/mkisofs

Add support for generating a Windows only tools ISO