[hitori] build: Add validation checks for the UI files

[Philip Withnall <pwithnall src gnome org>]

commit a2673166bde308c06fd4c636987e4dc8f0b07681
Author: Philip Withnall <philip tecnocode co uk>
Date:   Fri Dec 23 23:42:49 2016 +0000

    build: Add validation checks for the UI files

 Makefile.am  |   10 +++++++---
 configure.ac |    4 ++++
 2 files changed, 11 insertions(+), 3 deletions(-)
---
diff --git a/Makefile.am b/Makefile.am
index f82554d..54f47f5 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -84,13 +84,17 @@ CLEANFILES = src/hitori-resources.c
 EXTRA_DIST += src/hitori.gresource.xml
 
 # UI & CSS files
-dist_noinst_DATA = \
+ui_data = \
        data/hitori-menus.ui \
        data/hitori.ui \
+       $(NULL)
+dist_noinst_DATA = \
+       $(ui_data) \
        data/hitori.css
 
-check-builder: $(ui_DATA)
-       xmllint --nonet --noblanks --noout --relaxng /opt/gnome3/source/gtk+/gtk/gtkbuilder.rng $^
+check-builder: $(ui_data)
+       [ "$(XMLLINT)" == "" ] || \
+       $(XMLLINT) --nonet --noblanks --noout --relaxng $(GTK_PREFIX)/share/gtk-3.0/gtkbuilder.rng $^
 check-local: check-builder
 
 # GSettings
diff --git a/configure.ac b/configure.ac
index f7fbb9d..ae000fd 100644
--- a/configure.ac
+++ b/configure.ac
@@ -48,6 +48,10 @@ PKG_CHECK_MODULES([GENERAL],[
   gmodule-2.0 cairo >= 1.4
 ])
 
+# GTK+ prefix for gtkbuilder.rng
+PKG_CHECK_VAR([GTK_PREFIX],[gtk+-3.0],[prefix])
+AC_PATH_PROG([XMLLINT],[xmllint])
+
 # Output!
 AC_CONFIG_FILES([
 Makefile