[gxml] Added meson options

[Daniel Espinosa Ortiz <despinosa src gnome org>]

commit e676d1386052d6434a6a077e2a07d05c3f8cb2e0
Author: Daniel Espinosa <esodan gmail com>
Date:   Wed Aug 22 11:40:15 2018 -0500

    Added meson options

 meson_options.txt | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/meson_options.txt b/meson_options.txt
new file mode 100644
index 0000000..ac3306b
--- /dev/null
+++ b/meson_options.txt
@@ -0,0 +1 @@
+option('enable-tnode-tests', type : 'boolean', value : false, description : 'Enable TNode classes unit 
tests')
\ No newline at end of file