I put some notes on trac.  I’ll see about updating build notes later.  

I did find some stuff in the Mach linker that needs to be handled differently on gcc vs clang on Mac.  And likely needs a patch so it also builds clean with gcc 

On Thu, Dec 28, 2017 at 10:26 AM Ben Gamari <ben@smart-cactus.org> wrote:
Carter Schonwald <carter.schonwald@gmail.com> writes:

> digging around in configure.ac it looks like i need to set CC_STAGE0 env
> variable to my desired CC :)
>
> hope this helps other folks... but it definiely seems like the current
> logic for CC_STAGE0 is more brittle than for CC
>
Indeed, I've realized over the last few weeks in attempts to
cross-compile GHC that our configure script is a bit... let's say
peculiar in several respects.

Do record your findings on the Wiki. They will be much easier to find
there than buried on ghc-devs.

Cheers,

- Ben