Enable EliminateAvailableExternally pass in the LTO pipeline.
Enable EliminateAvailableExternally pass in the LTO pipeline.

Summary:
For LTO we need to enable this pass in the LTO pipeline,
as it is skipped during the "-flto -c" compile step (when PrepareForLTO is
set).

Reviewers: rnk

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D11919

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@244622 91177308-0d34-0410-b5e6-96231b3b80d8

GPUOpen-Drivers/llvm,apple/swift-llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,apple/swift-llvm,llvm-mirror/llvm,llvm-mirror/llvm,apple/swift-llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm