Disable threads in boost

Enabling threads in asio adds unnecessary locks that are not required in
a single threaded applications, and increases the binary size.

Change-Id: Iddd91913e941e9da64248f56196b244d5c04a5a8
Signed-off-by: Ed Tanous <ed@tanous.net>
diff --git a/meson.build b/meson.build
index 7ca6c9b..f28fd1e 100644
--- a/meson.build
+++ b/meson.build
@@ -9,7 +9,14 @@
     version: '1.0',
 )
 
-add_project_arguments('-Wno-psabi', language: 'cpp')
+add_project_arguments(
+    [
+        '-Wno-psabi',
+        '-DBOOST_ASIO_DISABLE_THREADS',
+        '-DBOOST_ASIO_NO_DEPRECATED',
+    ],
+    language: 'cpp'
+)
 
 deps = [dependency('libsystemd', version : '>=221'),
         dependency('systemd'),