libc should use O_CLOEXEC when opening files for its own use.

Change-Id: I159f1d57e0ca090d837f57854fcef5879b8b8248
diff --git a/libc/bionic/debug_mapinfo.cpp b/libc/bionic/debug_mapinfo.cpp
index d83799a..698ab6b 100644
--- a/libc/bionic/debug_mapinfo.cpp
+++ b/libc/bionic/debug_mapinfo.cpp
@@ -71,7 +71,7 @@
   struct mapinfo_t* milist = NULL;
   char data[1024]; // Used to read lines as well as to construct the filename.
   snprintf(data, sizeof(data), "/proc/%d/maps", pid);
-  FILE* fp = fopen(data, "r");
+  FILE* fp = fopen(data, "re");
   if (fp != NULL) {
     while (fgets(data, sizeof(data), fp) != NULL) {
       mapinfo_t* mi = parse_maps_line(data);