[glib] meson: don't error out if xmllint is not found

[Tim-Philipp Müller <tpm src gnome org>]

commit a1fdae8afcb9abe9327a367ffae8deee9c99400f
Author: Tim-Philipp Müller <tim centricular com>
Date:   Thu Aug 3 19:23:25 2017 +0100

    meson: don't error out if xmllint is not found
    
    Only needed for glib/tests and entirely optional.

 glib/tests/meson.build |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/glib/tests/meson.build b/glib/tests/meson.build
index f11869e..a78d9c0 100644
--- a/glib/tests/meson.build
+++ b/glib/tests/meson.build
@@ -170,7 +170,7 @@ executable('test-spawn-echo', 'test-spawn-echo.c',
 
 # some testing of gtester functionality
 if not meson.is_cross_build() and host_system != 'windows'
-  xmllint = find_program('xmllint')
+  xmllint = find_program('xmllint', required: false)
   if xmllint.found()
     tmpsample_xml = custom_target('tmpsample.xml',
       output : 'tmpsample.xml',