hsc2hs #const U_NO_NUMERIC does not work with --cross-compile

This seems to be because the way `--cross-compile` checks if something is valid is by using it as an array size, but this constant is a double, so that's not allowed.

In general #const says it is for longs, but this constant could be a long, it's just cast to double for some reason.

I'm working around it for now by doing the hsc2hs call without `--cross-compile` (since the constants are the same on my host system) and building against the result.