As far as I can tell, Graphviz will not compile with a version of Pango in the
range [1, 1.22). Referencing the current Graphviz HEAD,
673f3161e838451f1b5579f9975d8dd0c4f3c647, this code in
plugin/pango/gvtextlayout_pango.c will not compile:

  #if !defined(_WIN32) && defined PANGO_VERSION_MAJOR && (PANGO_VERSION_MAJOR >= 1)
    span->yoffset_layout = pango_layout_get_baseline (layout) * textlayout_scale;
  #else
    …

The API function `pango_layout_get_baseline` was only introduced in Pango
1.22.0. This is most likely moot, as Pango 1.22.0 was released in September
2008. So it is unlikely anyone is attempting to compile Graphviz with a Pango
version prior to this.