[gnome-themes-standard] build: Make error on older GTK+ nicer

[Bastien Nocera <hadess src gnome org>]

commit 5444e49ac5b2baf6ad8676581a53bcbcafd5ea9d
Author: Bastien Nocera <hadess hadess net>
Date:   Wed Sep 7 17:34:26 2011 +0100

    build: Make error on older GTK+ nicer
    
    "configure: error: GTK+-3.0 is required to compile gnome-themes-standard"
    
    But I have something even newer than that! And it's definitely
    installed, I hear you cry. Yeah, it wasn't you, it was us. No, really,
    it was us.
    
    "configure: error: GTK+ 3.1.18 is required to compile gnome-themes-standard"

 configure.ac |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 4adf17c..eef92da 100644
--- a/configure.ac
+++ b/configure.ac
@@ -28,8 +28,10 @@ AC_SUBST(GETTEXT_PACKAGE)
 AC_DEFINE_UNQUOTED([GETTEXT_PACKAGE],["$GETTEXT_PACKAGE"],[Gettext package])
 AM_GLIB_GNU_GETTEXT
 
-PKG_CHECK_MODULES(GTK, gtk+-3.0 >= 3.1.18 librsvg-2.0,,
-                  AC_MSG_ERROR([GTK+-3.0 is required to compile gnome-themes-standard]))
+GTK_VERSION_REQUIRED=3.1.18
+
+PKG_CHECK_MODULES(GTK, gtk+-3.0 >= $GTK_VERSION_REQUIRED librsvg-2.0,,
+                  AC_MSG_ERROR([GTK+ $GTK_VERSION_REQUIRED is required to compile gnome-themes-standard]))
 
 AC_SUBST(GTK_CFLAGS)
 AC_SUBST(GTK_LIBS)