irgen: don't emit debug metadata for locals

Summary:
The debug metadata we generate is wrong, and is
now causing build failures. This revision disables
the only llvm.dbg.declare calls we make.

(There is also a drive-by fix to CMakeLists.txt,
adding in a missing .go dependency.)

Fixes http://llvm.org/bugs/show_bug.cgi?id=22330

Reviewers: pcc

Reviewed By: pcc

Subscribers: dblaikie, llvm-commits

Differential Revision: http://reviews.llvm.org/D7222

llvm-svn: 227403