[gnome-builder] main: add missing locale.h include

[Christian Hergert <chergert src gnome org>]

commit c6709e02661f3ce6a938cd6f7dcb42a1d9424196
Author: Jürg Billeter <j bitron ch>
Date:   Thu Nov 7 09:38:11 2019 +0100

    main: add missing locale.h include

 src/main.c | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/src/main.c b/src/main.c
index 69176aad0..242f1937a 100644
--- a/src/main.c
+++ b/src/main.c
@@ -31,6 +31,7 @@
 #include <libide-greeter.h>
 #include <libide-gui.h>
 #include <libide-threading.h>
+#include <locale.h>
 #ifdef ENABLE_TRACING_SYSCAP
 # include <sysprof-capture.h>
 #endif