CGDebugInfo: Don't reuse a reference into a DenseMap if the DenseMap may be modified in between. (NFC)
CGDebugInfo: Don't reuse a reference into a DenseMap if the DenseMap may
be modified in between. (NFC)

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@248826 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang