fix another misuse of strncat

This has the potential to overflow "buffer" if the command line
is more than 4K.

Change-Id: Icdfed0d9d21804f290b75787ef3809e0475b14f0
diff --git a/toolbox/log.c b/toolbox/log.c
index f30e6a7..0bee19e 100644
--- a/toolbox/log.c
+++ b/toolbox/log.c
@@ -130,8 +130,8 @@
     buffer[0] = '\0';
     
     for (i = optind ; i < argc ; i++) {
-        strncat(buffer, argv[i], sizeof(buffer)-1);
-        strncat(buffer, " ", sizeof(buffer)-1);
+        strlcat(buffer, argv[i], sizeof(buffer)-1);
+        strlcat(buffer, " ", sizeof(buffer)-1);
     }
 
     if(buffer[0] == 0) {