meson.build: Allow skipping the systemd service

meson.build

@@ -9,13 +9,19 @@ project('qrtr',
         ])
 
 prefix = get_option('prefix')
-systemd = dependency('systemd')
 
+install_systemd_unit = get_option('systemd-service')
+systemd = dependency('systemd', required : install_systemd_unit)
+if systemd.found()
         systemd_system_unit_dir = get_option('systemd-unit-prefix')
         if systemd_system_unit_dir == ''
                 systemd_system_unit_dir = systemd.get_variable(
                         pkgconfig : 'systemdsystemunitdir',
                 pkgconfig_define: ['prefix', prefix])
+        else
+                message('Could not resolve systemd dependencies, skipping unit file')
+                install_systemd_unit = false
+        endif
 endif
 
 inc = include_directories('include')
@@ -23,6 +29,7 @@ subdir('lib')
 subdir('include')
 subdir('src')
 
+if systemd.found()
         systemd_unit_conf = configuration_data()
         systemd_unit_conf.set('prefix', prefix)
         configure_file(
@@ -30,3 +37,4 @@ configure_file(
                 output : 'qrtr-ns.service',
                 configuration : systemd_unit_conf,
                 install_dir : systemd_system_unit_dir)
+endif

meson_options.txt

@@ -2,3 +2,9 @@ option('systemd-unit-prefix',
   type: 'string',
   description: 'Directory for systemd system unit files'
 )
+
+option('systemd-service',
+  type: 'feature',
+  value: 'auto',
+  description: 'Whether or not the systemd service should be built'
+)