squash warnings in gtk headers

diff --git a/plugin/gtk/Makefile.am b/plugin/gtk/Makefile.am
index ffa4c04f230822ebec3f096c84a0436f816a1bc2..5bfd44a805fef10de719dde42af724bbaaff36a5 100644 (file)
--- a/plugin/gtk/Makefile.am
+++ b/plugin/gtk/Makefile.am
@@ -7,7 +7,7 @@ AM_CPPFLAGS = \
         -I$(top_srcdir)/lib/gvc \
         -I$(top_srcdir)/lib/cgraph \
         -I$(top_srcdir)/lib/cdt \
-       $(GTK_CFLAGS)
+        $(GTK_CFLAGS:-I%=-isystem%)
 
 if WITH_PANGOCAIRO
 if WITH_GTK