ThinLTOCodeGenerator: remove useless temporary file that was emitted.
ThinLTOCodeGenerator: remove useless temporary file that was emitted.

This was a remaining of a previous scheme where some IPOs were taking
place before we enter this code. This is not relevant anymore.

From: Mehdi Amini <mehdi.amini@apple.com>

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@268605 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm