The changes introduced in 2.12nb3 do indeed fix the build issues.  However,
now I get a version of 'dot' that does not render fonts properly when using
the png renderer.  Now matter what font I specify, all I can get out of it is
something that is probably Courier.  OTOH, the ps renderer gets the fonts
right.  I did not have this problem (with png) when I built with
CONFIGURE_ARGS+= --with-mylibgd, suggesting a libgd issue.

I did some experimenting, and I found that if I (re-)enable pangocairo, it
builds properly and the png renderer uses the fonts I specify.