[ModuleDependencyCollector] Use llvm::sys::fs::real_path (NFC)
[ModuleDependencyCollector] Use llvm::sys::fs::real_path (NFC)

Use the real_path implementation from llvm::sys::fs::real_path instead
of having a custom implementation in the ModuleDependencyCollector.

Differential revision: https://reviews.llvm.org/D57411

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@352605 91177308-0d34-0410-b5e6-96231b3b80d8

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