More cases where libc should use O_CLOEXEC.

Change-Id: Idfa111aeebc5deca2399dae919e8b72eb54c23c0
diff --git a/libc/bionic/dirent.cpp b/libc/bionic/dirent.cpp
index 7abc7f3..5e1c7a5 100644
--- a/libc/bionic/dirent.cpp
+++ b/libc/bionic/dirent.cpp
@@ -78,7 +78,7 @@
 }
 
 DIR* opendir(const char* path) {
-  int fd = open(path, O_RDONLY | O_DIRECTORY);
+  int fd = open(path, O_CLOEXEC | O_DIRECTORY | O_RDONLY);
   return (fd != -1) ? __allocate_DIR(fd) : NULL;
 }