[gn build] Add build files for opt and its dependency Transforms/Couroutines

Needed for check-lld.

Differential Revision: https://reviews.llvm.org/D55750


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@349324 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed