Andrew Farmer authored Apr 17, 2016 and Ben Gamari committed Apr 17, 2016

Prevent shared objects from being unloaded if cost centre stacks point
at the object. This will prevent segfault in #11776, but also prevents
objects from ever being unloaded when profiling. Pruning CCS tree will
enable that in another diff.

Test Plan: make TEST=linker_profiled, examine linker_profiled.run.stderr

Reviewers: austin, simonmar, bgamari

Reviewed By: simonmar, bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2069

GHC Trac Issues: #11776

(cherry picked from commit 36a0b6dc)