Remove unnecessary bits from the documentation build rules

We don't need to list the source files as we use a glob rule in the
Doxyfile itself.

doc/meson.build

@@ -1,21 +1,8 @@
-doc_sources = [
-  join_paths(meson.source_root(), 'include/epoxy/gl.h'),
-  join_paths(meson.source_root(), 'include/epoxy/egl.h'),
-  join_paths(meson.source_root(), 'include/epoxy/glx.h'),
-  join_paths(meson.source_root(), 'include/epoxy/wgl.h'),
-
-  join_paths(meson.source_root(), 'src/dispatch_common.c'),
-  join_paths(meson.source_root(), 'src/dispatch_egl.c'),
-  join_paths(meson.source_root(), 'src/dispatch_glx.c'),
-  join_paths(meson.source_root(), 'src/dispatch_wgl.c'),
-]
-
 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())
-doxyfile_conf.set('DOC_SOURCES', ' '.join(doc_sources))
 
 doxyfile = configure_file(input: 'Doxyfile.in',
                           output: 'Doxyfile',
@@ -25,7 +12,7 @@ doxyfile = configure_file(input: 'Doxyfile.in',
 docdir = join_paths(epoxy_datadir, 'doc')
 
 html_target = custom_target('epoxy-docs',
-                            input: [ doxyfile ] + doc_sources,
+                            input: [ doxyfile ],
                             output: [ 'html' ],
                             command: [ doxygen, doxyfile ],
                             install: true,