Help with GUB, or manual cross-compile

[Chris Yate]

Following up a conversation on the user list, as this might be a better
place to ask... I think we've established that the only way to compile for
Windows is to use GUB on Linux to cross-compile for mingw. Well, GUB barfs
all the time here. I could start posting chunks of GUB log messages, but I
don't feel that's really useful at this point -- if someone is able to help
diagnose the problem we can look into that!

First, to make sure I'm not wasting my time, can somebody suggest what
build platform and configuration I need to successfully cross-compile
Lilypond for Windows? I've tried a number of different Ubuntu versions,
either VMs or linux running directly on the metal. I've had to install a
few libraries (mpf, mpc, zlib etc.) from apt in order to get a step further
in GUB. I've also installed the mingw g++ packages, though I'm not sure
whether that is relevant.

Also, do I need to anything more than:
    $ bin/gub mingw::lilypond
?

Alternatively, I'm sure it should be possible (possibly easy) to
./configure the lilypond source code directly for cross compilation. If
someone has a quick solution for how to do that, I'd be really grateful of
it.

Context: I'm getting seriously fed up with a bug in Lilypond that's causing
the build of scores of larger than smallish size to crash. It's a very
repeatable assertion failure, "Line 1180 in Page-Breaking.cc". However,
I've not found it easy to create a reliable "minimal" example for this. It
only seems to happen in reasonably complicated scores with 10+ staves and a
few pages.  In any case, unless I can compile this for Windows I wouldn't
be able to investigate the problem at all.

Thanks in advance!

Chris