Ben Gamari authored Dec 08, 2016 and Ben Gamari committed Dec 08, 2016

D1290 places string constants in the `.rodata.str` section with `aMS`
section flags so that the linker can merge them. However, it seems that
ld doesn't understand these flags. It appears that `gcc
-fmerge-constants` uses the `dr` flags on Windows. Make GHC do the same.

Test Plan: Validate on Windows

Reviewers: xnyhps, austin, Phyx

Reviewed By: Phyx

Subscribers: thomie, trommler

Differential Revision: https://phabricator.haskell.org/D2797

GHC Trac Issues: #9577