libsoup: Fix build on SmartOS


(otis)

$NetBSD: patch-meson.build,v 1.1 2019/08/19 20:03:09 otis Exp $

--- meson.build.orig	2019-08-19 19:41:36.080576330 +0000
+++ meson.build
@@ -31,6 +31,11 @@ default_source_flag = [
 
 add_project_arguments(default_source_flag, language: 'c')
 
+# Needed for build on SmartOS
+if host_system == 'sunos'
+      add_project_arguments('-D__EXTENSIONS__', language: 'c')
+endif
+
 common_flags = [
   '-DHAVE_CONFIG_H',
 ]