Forcing XPG5 removes locale_t from <locale.h>.
This breaks including libintl.h, since gettext is built with locale_t
in view.

Index: meson.build
--- meson.build.orig
+++ meson.build
@@ -122,7 +122,7 @@ configure_file(
 add_global_arguments('-DAS_COMPILATION', language : 'c')
 
 # Needed for realpath()
-add_project_arguments('-D_XOPEN_SOURCE=500', language : 'c')
+#add_project_arguments('-D_XOPEN_SOURCE=500', language : 'c')
 
 subdir('libappstream-glib')
 subdir('data')
