This library is kind of a mess right now. There is a library that builds with
vex and a different one that builds with vext. Build them each by doing
this:
cabal build --project-file cabal.vex.project --builddir dist-vex all
cabal build --project-file cabal.vext.project --builddir dist-vext all
And the run the tests (which use the vex part) with:
./scripts/runtests