Getting other portfile's header / library paths inside another?

[Michael Dickens]

Is there a way -inside a portfile- to determine the header or library
search path for another port (e.g., as provided by "pkg-config
--cflags-only-I dbus-1")?  For example, use 'pkg-config' to return
information & save that into a variable locally for manipulation?  Right
now I'm hard-coding heading include and library search paths for
dependency ports (into qt4-mac), and it seems to me that a better
solution would be dynamic determination.  Thanks in advance! - MLD