meson.build: Allow skipping the systemd service

meson.build

@@ -9,24 +9,32 @@ project('qrtr',
         ])
 
 prefix = get_option('prefix')
-systemd = dependency('systemd')
 
-systemd_system_unit_dir = get_option('systemd-unit-prefix')
-if systemd_system_unit_dir == ''
-        systemd_system_unit_dir = systemd.get_variable(
-                pkgconfig : 'systemdsystemunitdir',
+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')
 subdir('lib')
 subdir('include')
 subdir('src')
 
-systemd_unit_conf = configuration_data()
-systemd_unit_conf.set('prefix', prefix)
-configure_file(
-               input : 'qrtr-ns.service.in',
-               output : 'qrtr-ns.service',
-               configuration : systemd_unit_conf,
-               install_dir : systemd_system_unit_dir)
+if systemd.found()
+        systemd_unit_conf = configuration_data()
+        systemd_unit_conf.set('prefix', prefix)
+        configure_file(
+                input : 'qrtr-ns.service.in',
+                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'
+)