fix regression in propagating depends in gtkdoc

In commit 68e684d51f the function
signature was changed, but several places did not adapt. Additionally,
we now totally dropped the in-place update of gtkdoc's sole source of
dependencies, but didn't propagate them upward to assign the newly
collected dependencies anywhere.

Fixes building gtkdoc with internal dependencies and failing when
specified directly (when building the 'all' target with sufficiently
random parallelism, deps may be built on time).

Fixes:
  https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1008382
  https://gitlab.gnome.org/GNOME/libmediaart/-/issues/4

mesonbuild/modules/gnome.py

@@ -674,6 +674,7 @@ class GnomeModule(ExtensionModule):
                         external_ldflags.update(libdepflags[2])
                         external_ldflags_nodedup += libdepflags[3]
                         gi_includes.update(libdepflags[4])
+                        depends.extend(libdepflags[5])
                 extdepflags = self._get_dependencies_flags(dep.ext_deps, state, depends, include_rpath,
                                                            use_gir_args, True)
                 cflags.update(extdepflags[0])
@@ -681,6 +682,7 @@ class GnomeModule(ExtensionModule):
                 external_ldflags.update(extdepflags[2])
                 external_ldflags_nodedup += extdepflags[3]
                 gi_includes.update(extdepflags[4])
+                depends.extend(libdepflags[5])
                 for source in dep.sources:
                     if isinstance(source, GirTarget):
                         gi_includes.update([os.path.join(state.environment.get_build_dir(),
@@ -1456,8 +1458,10 @@ class GnomeModule(ExtensionModule):
         t_args.append(f'--expand-content-files={"@@".join(abs_filenames(kwargs["expand_content_files"]))}')
         t_args.append(f'--ignore-headers={"@@".join(kwargs["ignore_headers"])}')
         t_args.append(f'--installdir={"@@".join(kwargs["install_dir"])}')
-        t_args += self._get_build_args(kwargs['c_args'], kwargs['include_directories'],
-                                       kwargs['dependencies'], state, depends)
+        build_args, new_depends = self._get_build_args(kwargs['c_args'], kwargs['include_directories'],
+                                                       kwargs['dependencies'], state, depends)
+        t_args.extend(build_args)
+        new_depends.extend(depends)
         custom_target = build.CustomTarget(
             targetname,
             state.subdir,
@@ -1466,7 +1470,7 @@ class GnomeModule(ExtensionModule):
             [],
             [f'{modulename}-decl.txt'],
             build_always_stale=True,
-            extra_depends=depends,
+            extra_depends=new_depends,
         )
         alias_target = build.AliasTarget(targetname, [custom_target], state.subdir, state.subproject)
         if kwargs['check']:
@@ -1484,10 +1488,11 @@ class GnomeModule(ExtensionModule):
     def _get_build_args(self, c_args: T.List[str], inc_dirs: T.List[T.Union[str, build.IncludeDirs]],
                         deps: T.List[T.Union[Dependency, build.SharedLibrary, build.StaticLibrary]],
                         state: 'ModuleState',
-                        depends: T.Sequence[T.Union[build.BuildTarget, 'build.GeneratedTypes']]) -> T.List[str]:
+                        depends: T.Sequence[T.Union[build.BuildTarget, 'build.GeneratedTypes']]) -> T.Tuple[
+                                T.List[str], T.List[T.Union[build.BuildTarget, 'build.GeneratedTypes', 'FileOrString', build.StructuredSources]]]:
         args: T.List[str] = []
         cflags = c_args.copy()
-        deps_cflags, internal_ldflags, external_ldflags, *_ = \
+        deps_cflags, internal_ldflags, external_ldflags, _nodedup, _gi_includes, new_depends = \
             self._get_dependencies_flags(deps, state, depends, include_rpath=True)
 
         cflags.extend(deps_cflags)
@@ -1512,7 +1517,7 @@ class GnomeModule(ExtensionModule):
         if ldflags:
             args += ['--ldflags=%s' % join_args(ldflags)]
 
-        return args
+        return args, new_depends
 
     @noKwargs
     @typed_pos_args('gnome.gtkdoc_html_dir', str)