Merging r340125:

------------------------------------------------------------------------
r340125 | lhames | 2018-08-18 11:38:37 -0700 (Sat, 18 Aug 2018) | 6 lines

[RuntimeDyld] Fix a bug in RuntimeDyld::loadObjectImpl that was over-allocating
space for common symbols.

Patch by Dmitry Sidorov. Thanks Dmitry!

Differential revision: https://reviews.llvm.org/D50240
------------------------------------------------------------------------

llvm-svn: 348555