It isn't necessary now that Cabal can find gcc in the new layout, and
it was taking a long time (2.5s on Windows every time you start up
make in the testsuite)

Since we're about to remove that primop. Define a version locally (using
undefined). It does not have to work since we only need it for its type.

it's a generic test, so I named it after the operation rather than the
ticket

The 'threadsafe' one is now deprecated.

This works around a problem on (old?) Fedora systems, where "locale -a"
lists every locale that /might/ exist, rather than only those that /do/
exist.

Two of the modules now get compiled in the opposite order