circleci: Build with in-tree GMP on Darwin
circleci: Build with in-tree GMP on Darwin

Fixes #15404.

(cherry picked from commit 578012be13eb1548050d51c0a23bd1a98423f03e)

sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc