[gnome-builder] runner: improve max_fd discovery

[Christian Hergert <chergert src gnome org>]

commit 51f460d9540818193b44d26da5ea01bc6f73b47c
Author: Christian Hergert <chergert redhat com>
Date:   Fri Mar 24 04:36:43 2017 -0700

    runner: improve max_fd discovery
    
    We should be more vigilant in getting a proper FD number to map in.

 libide/runner/ide-runner.c |   15 +++++++++++----
 1 files changed, 11 insertions(+), 4 deletions(-)
---
diff --git a/libide/runner/ide-runner.c b/libide/runner/ide-runner.c
index 70714c1..e5c5203 100644
--- a/libide/runner/ide-runner.c
+++ b/libide/runner/ide-runner.c
@@ -1090,10 +1090,17 @@ ide_runner_take_fd (IdeRunner *self,
    */
   if (dest_fd < 0)
     {
-      if (priv->fd_mapping->len == 0)
-        dest_fd = 3;
-      else
-        dest_fd = g_array_index (priv->fd_mapping, FdMapping, priv->fd_mapping->len - 1).dest_fd + 1;
+      gint max_fd = 2;
+
+      for (guint i = 0; i < priv->fd_mapping->len; i++)
+        {
+          FdMapping *entry = &g_array_index (priv->fd_mapping, FdMapping, i);
+
+          if (entry->dest_fd > max_fd)
+            max_fd = entry->dest_fd;
+        }
+
+      dest_fd = max_fd + 1;
     }
 
   map.source_fd = source_fd;