[buoh] make xsltproc optional

[Jan Tojnar <jtojnar src gnome org>]

commit eb7f2594dde21050a776443d38bd895adb77d070
Author: Jan Tojnar <jtojnar gmail com>
Date:   Wed Jan 23 13:27:52 2019 +0100

    make xsltproc optional

 data/meson.build | 3 +--
 meson.build      | 1 +
 2 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/data/meson.build b/data/meson.build
index 7d6ecad..67590d0 100644
--- a/data/meson.build
+++ b/data/meson.build
@@ -8,8 +8,7 @@ ui_files = files(
   'ui/view-message.ui',
   'ui/window.ui',
 )
-xsltproc = find_program('xsltproc')
-if gtk_builder_tool.found()
+if gtk_builder_tool.found() and xsltproc.found()
   foreach ui : ui_files
     # gtk-builder-tool validate does not support custom widgets
     ui_for_validation = configure_file(
diff --git a/meson.build b/meson.build
index 613e25e..6b2e756 100644
--- a/meson.build
+++ b/meson.build
@@ -32,6 +32,7 @@ libxml2 = dependency('libxml-2.0', version: '>= 2.4.0')
 desktop_file_validate = find_program('desktop-file-validate', required: false)
 gtk_builder_tool = find_program('gtk-builder-tool', required: false)
 xmllint = find_program('xmllint', required: false)
+xsltproc = find_program('xsltproc', required: false)
 
 buoh_deps = [
   gtk,