Fix linux build.

llvm-svn: 298007
diff --git a/llvm/lib/Support/Unix/Path.inc b/llvm/lib/Support/Unix/Path.inc
index c1ffd1e..80bb1a4 100644
--- a/llvm/lib/Support/Unix/Path.inc
+++ b/llvm/lib/Support/Unix/Path.inc
@@ -486,7 +486,8 @@
     return;
 
   PathStr = PathStr.drop_front();
-  StringRef Expr = PathStr.take_until(path::is_separator);
+  StringRef Expr =
+      PathStr.take_until([](char c) { return path::is_separator(c); });
   StringRef Remainder = PathStr.substr(Expr.size() + 1);
   SmallString<128> Storage;
   if (Expr.empty()) {