Herbert Valerio Riedel authored Mar 05, 2018 and Ben Gamari committed Mar 06, 2018

This wasn't spotted rightaway in
8f0b2f5e
because the include-site deliberately ignored include-errors as
a Hack with the justification below:

> Hack. The file gmp/config.mk doesn't exist yet after running ./configure in
> the toplevel (ghc) directory. To let some toplevel make commands such as
> sdist go through, right after ./configure, don't consider this an error.

This may have contributed to #14891.

(cherry picked from commit df7ac37d)