Shea Levy authored Nov 29, 2016 and Ben Gamari committed Nov 29, 2016

On iOS, we use the pthread-based implementation of Itimer.c even for a
non-threaded RTS. Since 999c464d, this relies on synchronization
primitives like Mutex, so ensure those primitives are defined whenever
they are supported, even if !THREADED_RTS.

Fixes #12799.

Reviewers: erikd, austin, simonmar, bgamari

Reviewed By: simonmar, bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2712

GHC Trac Issues: #12799