Handle ctor/init_array initialization.

Hexagon was not calling InitializeELF and could not select between
ctors and init_array.

Phabricator revision: http://reviews.llvm.org/D6061

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@221156 91177308-0d34-0410-b5e6-96231b3b80d8