meson: add harfbuzz gobject dependency
When harfbuzz is built as a subproject, the gobject dep should be used to generate the gir.
The build was failing when the harfbuzz gir was not available system wide.
When harfbuzz is built as a subproject, the gobject dep should be used to generate the gir.
The build was failing when the harfbuzz gir was not available system wide.