sync code with last improvements from OpenBSD

dist/libepoxy/doc/meson.build

@@ -0,0 +1,25 @@
+doxyfile_conf = configuration_data()
+doxyfile_conf.set('PACKAGE_NAME', meson.project_name())
+doxyfile_conf.set('PACKAGE_VERSION', meson.project_version())
+doxyfile_conf.set('top_srcdir', meson.source_root())
+doxyfile_conf.set('top_builddir', meson.build_root())
+
+if find_program('dot', required: false).found()
+  doxyfile_conf.set('HAVE_DOT', 'YES')
+else
+  doxyfile_conf.set('HAVE_DOT', 'NO')
+endif
+
+doxyfile = configure_file(input: 'Doxyfile.in',
+                          output: 'Doxyfile',
+                          configuration: doxyfile_conf,
+                          install: false)
+
+docdir = join_paths(epoxy_datadir, 'doc')
+
+html_target = custom_target('epoxy-docs',
+                            input: [ doxyfile ],
+                            output: [ 'html' ],
+                            command: [ doxygen, doxyfile ],
+                            install: true,
+                            install_dir: join_paths(docdir, 'epoxy'))