build: Add meson build system

Reuse the generated dbus interface .xml files from fprintd to avoid
unnecessary copies.

doc/dbus/meson.build

@@ -0,0 +1,28 @@
+docbook_xml_header = custom_target('docbook_xml_header',
+    output: 'docbook-xml-header.xml',
+    command: [
+        'echo', '-n',
+        '<?xml version="1.0"?>',
+        '<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN" "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd">',
+    ],
+    capture: true,
+)
+
+dbus_interfaces_refs = []
+foreach interface_file: dbus_interfaces_files
+    basename = run_command('basename', interface_file.full_path(), '.xml').stdout().strip()
+    dbus_interfaces_refs += custom_target(basename + '_ref',
+        input: docbook_xml_header,
+        output: basename + '.ref.xml',
+        depends: interface_file,
+        capture: true,
+        command: [
+            bash, '-c',
+            'cat @INPUT@;' +
+            xsltproc.path() + ' @0@/@1@ '.format(
+                meson.source_root(),
+                files('spec-to-docbook.xsl')[0]) +
+            interface_file.full_path() + '| tail -n +2;',
+        ],
+    )
+endforeach