Alec Theriault authored Dec 05, 2018 and Ben Gamari committed Jan 23, 2019

Summary:
This adds top-level configure flags '--with-intree-gmp' and
'--with-framework-preferred', both of which are especially relevant
on MacOS.

Besides gaining two new flags, Hadrian also had to be taught what to
do with the 'framework' in .cabal files.

Test Plan:
./boot && ./configure --with-intree-gmp && ./hadrian/build.sh
./boot && ./configure --with-gmp-framework-preferred && ./hadrian/build.sh # on macos

Reviewers: carter, snowleopard, alpmestan, hvr, goldfire, bgamari

Subscribers: rwbarton, erikd

GHC Trac Issues: #16001

Differential Revision: https://phabricator.haskell.org/D5417