So yes, mock does the trick. Here are quick pointers for those interested.

It compiles srpms only, so you have to rpmbuild -bs specfile first.

If you don't want it to always fetch packages from a repository (very slow), install a local image:

mock --autocache --rebuildcache -r fedora-6-i386-core.cfg  init
mock --autocache -r fedora-6-i386-core.cfg clean

Don't forget to add yourself to the "mock" group.

Since I will only be compiling i386 packages with mock, I changed the default config:

cd /etc/mock
rm default.cfg
ln -s fedora-6-i386-core.cfg default.cfg

Then you can compile:

mock --no-clean --debug /phil/src/rpm/SRPMS/freetype-2.2.1-16bci.src.rpm

Here the command omits -r, so mock will assume it should use our default.cfg.

If you omit --no-clean, the chroot gets recreated everytime and makes compilation take much longer. If you omit --debug, you won't see much output at all.

Cheers!