policy: fix compilation on a variety of configurations

* Meson >=0.41.0, (unreleased) polkit 0.114+ don't use data_dirs argument
* Meson >=0.41.0, older polkit, use local ITS rules with data_dirs argument
* Meson <0.41.0, any polkit, use custom policy building rules

Later on when meson 0.41.0+ and polkit 0.114+ is in many stable distros
this commit can be reverted and dependencies updated.

Fixes: #107

policy/its/polkit.its

@@ -0,0 +1,8 @@
+<?xml version="1.0"?>
+<its:rules xmlns:its="http://www.w3.org/2005/11/its"
+           version="2.0">
+  <its:translateRule selector="//*" translate="no"/>
+  <its:translateRule selector="//action/description |
+                               //action/message"
+                     translate="yes"/>
+</its:rules>

policy/its/polkit.loc

@@ -0,0 +1,6 @@
+<?xml version="1.0"?>
+<locatingRules>
+  <locatingRule name="polkit policy" pattern="*.policy">
+    <documentRule localName="policyconfig" target="polkit.its"/>
+  </locatingRule>
+</locatingRules>

policy/meson.build

@@ -1,11 +1,43 @@
 install_data('org.freedesktop.fwupd.rules',
              install_dir : 'share/polkit-1/rules.d')
 
-i18n.merge_file(
-  input: 'org.freedesktop.fwupd.policy.in',
-  output: 'org.freedesktop.fwupd.policy',
-  type: 'xml',
-  po_dir: join_paths(meson.source_root(), 'po'),
-  install: true,
-  install_dir: join_paths(get_option('datadir'), 'polkit-1', 'actions')
-)
+#meson 0.41.0 added support for data_dirs argument
+if meson.version().version_compare('>=0.41.0')
+  #newer polkit has the ITS rules included
+  if polkit.version().version_compare('>0.113')
+    i18n.merge_file(
+      input: 'org.freedesktop.fwupd.policy.in',
+      output: 'org.freedesktop.fwupd.policy',
+      install: true,
+      install_dir: join_paths(get_option('datadir'), 'polkit-1', 'actions') ,
+      type: 'xml',
+      po_dir: join_paths(meson.source_root(), 'po')
+    )
+  #older polkit is missing ITS rules and will fail
+  else
+    i18n.merge_file(
+      input: 'org.freedesktop.fwupd.policy.in',
+      output: 'org.freedesktop.fwupd.policy',
+      install: true,
+      install_dir: join_paths(get_option('datadir'), 'polkit-1', 'actions') ,
+      type: 'xml',
+      data_dirs: join_paths(meson.source_root(), 'policy'),
+      po_dir: join_paths(meson.source_root(), 'po')
+    )
+  endif
+#older polkit and older meson, need to do some custom targets
+#see https://github.com/hughsie/fwupd/issues/107
+else
+  envbin = find_program('env')
+  gettext_data_dir = 'GETTEXTDATADIRS=' + join_paths(meson.source_root(), 'policy')
+  custom_target('org.freedesktop.fwupd.policy',
+    input: 'org.freedesktop.fwupd.policy.in',
+    output: 'org.freedesktop.fwupd.policy',
+    command: [envbin, gettext_data_dir, 'msgfmt', '--xml',
+              '--template', '@INPUT@',
+              '-d', join_paths(meson.source_root(), 'po'),
+              '-o', '@OUTPUT@'],
+    install: true,
+    install_dir: join_paths(get_option('datadir'), 'polkit-1', 'actions')
+   )
+endif