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

Change-Id: I159f1d57e0ca090d837f57854fcef5879b8b8248
diff --git a/libc/dns/net/getaddrinfo.c b/libc/dns/net/getaddrinfo.c
index 65fd1c1..a492318 100644
--- a/libc/dns/net/getaddrinfo.c
+++ b/libc/dns/net/getaddrinfo.c
@@ -2017,7 +2017,7 @@
 {
 
 	if (!*hostf)
-		*hostf = fopen(_PATH_HOSTS, "r" );
+		*hostf = fopen(_PATH_HOSTS, "re");
 	else
 		rewind(*hostf);
 }
@@ -2046,7 +2046,7 @@
 	assert(name != NULL);
 	assert(pai != NULL);
 
-	if (!*hostf && !(*hostf = fopen(_PATH_HOSTS, "r" )))
+	if (!*hostf && !(*hostf = fopen(_PATH_HOSTS, "re")))
 		return (NULL);
  again:
 	if (!(p = fgets(hostbuf, sizeof hostbuf, *hostf)))