Use the multiple argument form of path::append.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@185164 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Frontend/CompilerInvocation.cpp b/lib/Frontend/CompilerInvocation.cpp
index f362226..d8b4392 100644
--- a/lib/Frontend/CompilerInvocation.cpp
+++ b/lib/Frontend/CompilerInvocation.cpp
@@ -852,9 +852,7 @@
     llvm::sys::path::remove_filename(P); // Remove /bin   from foo/bin
 
     // Get foo/lib/clang/<version>/include
-    llvm::sys::path::append(P, "lib");
-    llvm::sys::path::append(P, "clang");
-    llvm::sys::path::append(P, CLANG_VERSION_STRING);
+    llvm::sys::path::append(P, "lib", "clang", CLANG_VERSION_STRING);
   }
 
   return P.str();