Bug 392722 - nsinstall chokes on double slashes in path

patch by benjamin@smedbergs.us  r=nelson

security/coreconf/nsinstall/nsinstall.c

@@ -125,8 +125,7 @@ mkdirs(char *path, mode_t mode)
 	fail("Null pointer or empty string passed to mkdirs()");
     while (*path == '/' && path[1] == '/')
 	path++;
-    while ((cp = strrchr(path, '/')) && cp[1] == '\0')
-	*cp = '\0';
+    for (cp = strrchr(path, '/'); cp && cp != path && *(cp - 1) == '/'; cp--);
     if (cp && cp != path) {
 	*cp = '\0';
 	if ((stat(path, &sb) < 0 || !S_ISDIR(sb.st_mode)) &&