libffi

[ElvishJerricco]

GHC uses libffi for Adjustor.c (and possibly other things?). But there is no libffi for WebAssembly. If possible, we should just provide a custom implementation of Adjustor.c like x86_64-linux and iOS, as it seems unreasonable to add WebAssembly support to libffi.

[ElvishJerricco]

Looks like we might be able to just use UseLibFFIForAdjustors = NO in GHC to skip this problem altogether.

[ElvishJerricco]

Punting for now with the above suggestion.