Fix "ptsname is not thread-safe; use ptsname_r instead" build break.

Change-Id: I8fdca8e85056e99e943bdcf93a48574d76addcdc
diff --git a/logwrapper/logwrap.c b/logwrapper/logwrap.c
index d47c9b5..3a6276e 100644
--- a/logwrapper/logwrap.c
+++ b/logwrapper/logwrap.c
@@ -477,7 +477,6 @@
     pid_t pid;
     int parent_ptty;
     int child_ptty;
-    char *child_devname = NULL;
     struct sigaction intact;
     struct sigaction quitact;
     sigset_t blockset;
@@ -498,8 +497,9 @@
         goto err_open;
     }
 
+    char child_devname[64];
     if (grantpt(parent_ptty) || unlockpt(parent_ptty) ||
-            ((child_devname = (char*)ptsname(parent_ptty)) == 0)) {
+            ptsname_r(parent_ptty, child_devname, sizeof(child_devname)) != 0) {
         ERROR("Problem with /dev/ptmx\n");
         rc = -1;
         goto err_ptty;