--- llvm/projects/compiler-rt/lib/sanitizer_common/sanitizer_mac.cpp.orig	2020-05-14 15:13:45.000000000 -0700
+++ llvm/projects/compiler-rt/lib/sanitizer_common/sanitizer_mac.cpp	2020-05-14 15:17:03.000000000 -0700
@@ -111,6 +111,11 @@
 #define VM_MEMORY_SANITIZER 99
 #endif
 
+// From <sys/spawn.h> but not in some SDKs
+#ifndef POSIX_SPAWN_CLOEXEC_DEFAULT
+#define	POSIX_SPAWN_CLOEXEC_DEFAULT	0x4000
+#endif
+
 // XNU on Darwin provides a mmap flag that optimizes allocation/deallocation of
 // giant memory regions (i.e. shadow memory regions).
 #define kXnuFastMmapFd 0x4