message: Fix PathMappingList tests on windows
  The tests added in r332842 don't work on windows, because they do path
  comparisons on strings, and on windows, the paths coming out of the
  mappings had backslashes in them.
  This switches comparisons to FileSpecs, so the results come out right.
diff: @@ -17,13 +17,14 @@ using namespace lldb_private;
  namespace {
  struct Matches {
  - ConstString original;
  - ConstString remapped;
  - Matches(const char *o, const char *r) : original(o),
  - remapped(r) {}
  + FileSpec original;
  + FileSpec remapped;
  + Matches(const char *o, const char *r)
  + : original(o, false), remapped(r, false) {}
  };
  +} // namespace
  - void TestPathMappings(const PathMappingList &map,
  +static void TestPathMappings(const PathMappingList &map,
  llvm::ArrayRef<Matches> matches,
  llvm::ArrayRef<ConstString> fails) {
  ConstString actual_remapped;
  @@ -31,18 +32,16 @@ namespace {
  EXPECT_FALSE(map.RemapPath(fail, actual_remapped));
  }
  for (const auto &match : matches) {
  - FileSpec orig_spec(match.original.GetStringRef(), false);
  - std::string orig_normalized = orig_spec.GetPath();
  - EXPECT_TRUE(map.RemapPath(match.original, actual_remapped));
  - EXPECT_EQ(actual_remapped, match.remapped);
  - FileSpec remapped_spec(match.remapped.GetStringRef(), false);
  + std::string orig_normalized = match.original.GetPath();
  + EXPECT_TRUE(
  + map.RemapPath(ConstString(match.original.GetPath()), actual_remapped));
  + EXPECT_EQ(FileSpec(actual_remapped.GetStringRef(), false), match.remapped);
  FileSpec unmapped_spec;
  - EXPECT_TRUE(map.ReverseRemapPath(remapped_spec, unmapped_spec));
  + EXPECT_TRUE(map.ReverseRemapPath(match.remapped, unmapped_spec));
  std::string unmapped_path = unmapped_spec.GetPath();
  EXPECT_EQ(unmapped_path, orig_normalized);
  }
  }
  -}
  TEST(PathMappingListTest, RelativeTests) {
  Matches matches[] = {
  