meson: check the value of has-plugins and build-hotdoc key
If 'has-plugins' and 'build-hotdoc' keys exist in build_infos, check their values too. With this change, the condition can be selected by changing the value of the key.
If 'has-plugins' and 'build-hotdoc' keys exist in build_infos, check their values too. With this change, the condition can be selected by changing the value of the key.