The unstable image seemed to cause problems recently.
We should just use the default image and fetch Cygwin ourselves.
Also added caching of the Cygwin files and simplified the script a bit.
Adds a configuration file to facilitate build of Mono with Cygwin
on Appveyor Windows-based build workers.
Dependencies are installed on a clean Appveyor build image for
each build and the result of the 'make install' step is stored
as a build output 'artifact' for further testing or deployment.
Signed-off-by: Alex J Lennon <ajlennon@dynamicdevices.co.uk>
