This change seems to speed up LLD a bit if it has a lot of mergeable
sections. The number is below. It's not too bad for a small patch.
Time to link Clang (debug build):
w/o patch 6.3696 seconds
w/patch 6.2746 seconds (-1.5%)
Differential Revision: http://reviews.llvm.org/D19933
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@268698 91177308-0d34-0410-b5e6-96231b3b80d8