[asan] Add a missing include.

llvm-svn: 150382
diff --git a/compiler-rt/lib/asan/interception/interception_linux.cc b/compiler-rt/lib/asan/interception/interception_linux.cc
index db43e81..32361e2 100644
--- a/compiler-rt/lib/asan/interception/interception_linux.cc
+++ b/compiler-rt/lib/asan/interception/interception_linux.cc
@@ -14,6 +14,7 @@
 
 #ifdef __linux__
 
+#include <stddef.h> // for NULL
 #include <dlfcn.h>  // for dlsym
 
 namespace __interception {