Update clang to r339409.

Change-Id: I800772d2d838223be1f6b40d490c4591b937fca2
diff --git a/linux-x64/clang/include/llvm/ADT/ImmutableMap.h b/linux-x64/clang/include/llvm/ADT/ImmutableMap.h
index 10d1e1f..cbc27ff 100644
--- a/linux-x64/clang/include/llvm/ADT/ImmutableMap.h
+++ b/linux-x64/clang/include/llvm/ADT/ImmutableMap.h
@@ -114,12 +114,13 @@
 
     ImmutableMap getEmptyMap() { return ImmutableMap(F.getEmptyTree()); }
 
-    ImmutableMap add(ImmutableMap Old, key_type_ref K, data_type_ref D) {
+    LLVM_NODISCARD ImmutableMap add(ImmutableMap Old, key_type_ref K,
+                                    data_type_ref D) {
       TreeTy *T = F.add(Old.Root, std::pair<key_type,data_type>(K,D));
       return ImmutableMap(Canonicalize ? F.getCanonicalTree(T): T);
     }
 
-    ImmutableMap remove(ImmutableMap Old, key_type_ref K) {
+    LLVM_NODISCARD ImmutableMap remove(ImmutableMap Old, key_type_ref K) {
       TreeTy *T = F.remove(Old.Root,K);
       return ImmutableMap(Canonicalize ? F.getCanonicalTree(T): T);
     }