[tracker] meson: NetworkManager should be an optional dep

[Sam Thursfield <sthursfield src gnome org>]

commit 39f51e2a926ea7b29e22a0b5083bf5c4e44a7252
Author: Sam Thursfield <sam thursfield codethink co uk>
Date:   Wed Sep 27 12:48:09 2017 +0100

    meson: NetworkManager should be an optional dep

 meson.build |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/meson.build b/meson.build
index f35d53c..f955ea9 100644
--- a/meson.build
+++ b/meson.build
@@ -28,7 +28,7 @@ icu_uc = dependency('icu-uc', version: '> 4.8.1.1', required: false)
 json_glib = dependency('json-glib-1.0', version: '>= 1.0', required: true)
 libsoup = dependency('libsoup-2.4', version: '> 2.40', required: true)
 libxml2 = dependency('libxml-2.0', version: '> 2.6')
-network_manager = dependency('libnm')
+network_manager = dependency('libnm', required: false)
 sqlite = dependency('sqlite3', version: '>' + sqlite_required)
 
 libmath = cc.find_library('m')