diff --git a/llvm/utils/gn/secondary/llvm/include/llvm/Config/BUILD.gn b/llvm/utils/gn/secondary/llvm/include/llvm/Config/BUILD.gn
--- a/llvm/utils/gn/secondary/llvm/include/llvm/Config/BUILD.gn
+++ b/llvm/utils/gn/secondary/llvm/include/llvm/Config/BUILD.gn
@@ -380,8 +380,12 @@
     # that \n is a literal '\' followed by a literal 'n', not a newline
     # character.  (write_cmake_config.py replaces that with a real newline).
     value = ""
-    foreach(target, all_targets) {
-      value = "$value${invoker.value}($target)\n"
+    if (all_targets != []) {
+      foreach(target, all_targets) {
+        value = "$value${invoker.value}($target)\n"
+      }
+    } else {
+      not_needed(invoker, [ "value" ])
     }
     values = [ "${invoker.key}=$value" ]
   }