[libgsystem] GSSubprocess: Use #ifdef, not #if for GLIB_COMPILATION

[Colin Walters <walters src gnome org>]

commit be1b3b9d3dbfacf15ede143de377452a92976468
Author: Colin Walters <walters verbum org>
Date:   Thu May 16 13:18:15 2013 -0400

    GSSubprocess: Use #ifdef, not #if for GLIB_COMPILATION
    
    It's not defined normally, and this triggers -Wundef which some
    projects make into an error.

 gsystem-subprocess.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/gsystem-subprocess.c b/gsystem-subprocess.c
index be23e21..ab5bbb7 100644
--- a/gsystem-subprocess.c
+++ b/gsystem-subprocess.c
@@ -209,7 +209,7 @@ gs_subprocess_unix_queue_waitpid (GSSubprocess  *self)
   GMainContext *worker_context;
   GSource *waitpid_source;
 
-#if GLIB_COMPILATION
+#ifdef GLIB_COMPILATION
   worker_context = GLIB_PRIVATE_CALL (g_get_worker_context) ();
 #else
   worker_context = g_main_context_get_thread_default ();