Fix slashes in path references in -Rmodule-import test from r355477
Fix slashes in path references in -Rmodule-import test from r355477

Fixup for r355477 to fix the Windows bot:
  http://lab.llvm.org:8011/builders/llvm-clang-x86_64-expensive-checks-win/builds/16217

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@355482 91177308-0d34-0410-b5e6-96231b3b80d8
(cherry picked from commit 38f1a525822288cc0aec7b2470edb61c2a2c0188)

apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang