[Driver] Follow-up to r211598, r211663. Do not build a dynamic linker path using sub-strings concatenation. Return the whole string explicitly.
[Driver] Follow-up to r211598, r211663. Do not build a dynamic linker
path using sub-strings concatenation. Return the whole string explicitly.

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@211665 91177308-0d34-0410-b5e6-96231b3b80d8

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