pkg-config files are becoming the norm to offer a library's settings. It would be very useful for rpm to process pkg-config files to add requires for -devel sub-packages. For example: libfoo uses libbar and libbaz libfoo-devel contains a pkg-config file that mentions "libbar and libbaz" libfoo-devel should automatically have added to its requires the libbar-devel and libbaz-devel packages. This would avoid problems when a package that uses libfoo but knows nothing of libbar or libbaz to have missing build requires.
Actually rpm already supports this, but generation of pkg-config requires has been disabled for now (provides are being added though) to avoid creating unsolvable dependencies. What's needed is either a) enabling the requires generation and a carefully ordered rebuild of all pkg-config enabled packages b) rebuild of all pkg-config enabled packages (in whatever order), enabling the requires generation and then another rebuild of the packages (in whatever order)
This bug appears to have been reported against 'rawhide' during the Fedora 10 development cycle. Changing version to '10'. More information and reason for this action is here: http://fedoraproject.org/wiki/BugZappers/HouseKeeping
Starting right now, pkg-config (and libtool) requires are getting generated too, rawhide only as this is bound to cause some amount of breakage from unsatisfied dependencies here and there.