[libsoup] Fix build on SmartOS/SunOS.

[Claudio Saavedra <csaavedra src gnome org>]

commit bee437ce7f04ffbd9243d0c56d23f05d5995f301
Author: Juraj Lutter <juraj lutter sk>
Date:   Tue Aug 20 13:40:35 2019 +0200

    Fix build on SmartOS/SunOS.
    
    - Properly #define __EXTENSIONS__
    - Add -lsocket link argument

 meson.build | 5 +++++
 1 file changed, 5 insertions(+)
---
diff --git a/meson.build b/meson.build
index dce0dde6..11e8aeec 100644
--- a/meson.build
+++ b/meson.build
@@ -31,6 +31,11 @@ default_source_flag = [
 
 add_project_arguments(default_source_flag, language: 'c')
 
+if host_system == 'sunos'
+      add_project_arguments('-D__EXTENSIONS__', language: 'c')
+      add_project_link_arguments('-lsocket', language: 'c')
+endif
+
 common_flags = [
   '-DHAVE_CONFIG_H',
 ]