[vte] tests: Silence unused variable warning

[Christian Persch <chpe src gnome org>]

commit f6c7c9e9ac6d1121c3ca6f1e0e0e4dfe4253eb3f
Author: Christian Persch <chpe src gnome org>
Date:   Fri Sep 28 12:17:40 2018 +0200

    tests: Silence unused variable warning

 src/vtetypes.cc | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/src/vtetypes.cc b/src/vtetypes.cc
index 92a9db28..ad5166ee 100644
--- a/src/vtetypes.cc
+++ b/src/vtetypes.cc
@@ -144,6 +144,8 @@ vte::color::rgb::to_string() const
 
 #ifdef MAIN
 
+#pragma GCC diagnostic ignored "-Wunused-variable"
+
 #include <glib.h>
 
 using namespace vte::grid;