Yes but does it work?

How I did it:
First, I'm running Linux *debian* on my pc. That helps a lot!

In debian (out of itchy and scratchy)
cd ~/src_sbox (this is a link to ~/src in scratchbox)
apt-get source libglib1.2-dev libgtk1.2-dev libogg-dev libvorbis-dev xmms

In scratchbox:
export CFLAGS="-O2 -fomit-frame-pointer -mcpu=arm1136jf-s -mfpu=vfp -mfloat-abi=softfp"
cd src
cd libglib1.2-dev
fakeroot debian/rules binary
cd ..
dpkg -i libglib*deb
cd libgtk1.2-dev
fakeroot debian/rules binary
cd ..
dpkg -i libgtk*deb
cd libvorbis-dev
fakeroot debian/rules binary
cd ..
dpkg -i libvorbis*deb
cd libogg-dev
fakeroot debian/rules binary
cd ..
dpkg -i libogg*deb
cd xmms-blabla
DEB_BUILD_OPTIONS="-no-oss -no-nls" fakeroot debian/rules binary
cd ..
dpkg -i xmms*deb

At this step, we know it installs in scratchbox.
Let's try it on the n800.
In debian
scp *.deb user@n800:/media/mmc2/deb

On the n800
cd /media/mmc2/deb
sudo gainroot
dpkg -i *.deb
LANG=C xmms


debian/rules specific:
1)
When you get COMPAT error, you have to add
export DH_COMPAT=4 in debian/rules
2) When you get error about incorrect substitutions (ex xmms-dev depends on xmms), you have to replace
Depends: xmms (= ${binary:Version}) by
Depends: xmms (= ${Source-Version})
3) I remove the line dh_installman. Hackers don't read docs.

xmms specific:
Some files are missing :
* install.sh, take it from another package (I took it from bonnie as I packaged it)
* depcomp, this is part of the autotools and on scratchbox they are not at the standard place.
cd /usr/share
ln -s /scratchbox/tools/autotools/automake-1.9/share/automake-1.9/ autotools-10
(cause xmms searches them in /usr/share/autotools-10 and scratchbox has them in /scratchbox/tools/autotools/automake-1.9/share/automake-1.9). This hack is a bit awfull.

xmms config, I changed debian/rules to:

I hard-coded no-alsa in configure (didn't find a way to pass it to ./configure)

That's about it..