Index: llvm/utils/gn/secondary/llvm/include/llvm/Config/BUILD.gn
===================================================================
--- llvm/utils/gn/secondary/llvm/include/llvm/Config/BUILD.gn
+++ llvm/utils/gn/secondary/llvm/include/llvm/Config/BUILD.gn
@@ -152,11 +152,8 @@
     ]
   }
 
-  if (current_os == "linux") {
-    values += [ "HAVE_VALGRIND_VALGRIND_H=1" ]
-  } else {
-    values += [ "HAVE_VALGRIND_VALGRIND_H=" ]
-  }
+  # Even Linux systems often don't have valgrind.h, so default it to off.
+  values += [ "HAVE_VALGRIND_VALGRIND_H=" ]
 
   if (current_os == "mac") {
     values += [