[webkit-gtk] JHBuild now used for testing

[Martin Robinson]

Hello WebKittens,

For as long as I have been involved in the project we have had a
problem where tests produce different results on different machines.
No amount of fiddling with fontconfig settings has been able to
counter the discrepancies between different versions of cairo and
freetype.

During the ongoing WebKitGTK+ hackfest, Gustavo and I have opted for
what I consider the 'nuclear' option. We have made jhbuild a
dependency for running layout tests. You can initialize the jhbuld
setup by calling ./Tools/Script/update-webkitgtk-libs. If you haven't
done this, it will happen automatically the next time you run
build-webkit or run-webkit-tests. You may need to do a clean build
after the first time this happens.

Important information:
* The jhbuild module and rc file are stored in ./Tools/gtk.
* You need to run update-wekbitgtk-libs manually when we change the
module file. We may eventually make this automatic, but it we
considered it more conservative to let things stabilize a bit.
* The switch has been a little bumpy, so don't be surprised if there's
breakage at first. If you run into a problem, file a bug or poke
mrobinson or kov directly via IRC.
* We are still in the process of discovering exactly what dependencies
affect test output, so we will be adding modules to the build as time
passes.

Soon, you should be able to get very close to 100% passage with any
machine. We should consider tests that pass on the bots and fail
locally or vice-versa a bug from now on.

--Martin