build: Update gtk-doc generation to meson changes

After updating our use of link_with/link_whole for meson-0.52.0 we
accidentally broke gtk-doc generation.

Before c8b862b4 gnome_builder_deps
included link_whole calls to all our libide static libraries. Because we
changed those calls to link_with, libide_gtk_doc was no longer linking
properly.

To solve the above we now use gnome_builder_static, which is a list of
all our internal libide static libraries and can be used as an argument
to link_whole, just like we do in the gnome_builder target.

Fixes: #1063

doc/sdk/meson.build

@@ -30,7 +30,7 @@ docpath = join_paths(get_option('datadir'), 'gtk-doc', 'html')
 
 libide_gtk_doc = shared_library('ide-gtk-doc',
             c_args: libide_args + release_args,
-      dependencies: gnome_builder_deps,
+        link_whole: gnome_builder_static,
 )
 
 libide_gtk_doc_dep = declare_dependency(