I don't see anything hardcoded in there that's any different to gtk/glib or any of the others I checked.

$ more /usr/lib64/pkgconfig/gupnp-vala-1.0.pc
prefix=/usr
exec_prefix=${prefix}
libdir=${exec_prefix}/lib
includedir=${prefix}/include

Name: gupnp-vala-1.0
Description: Vala bindings for GUPnP
Version: 0.5.3

$ pkg-config --variable=libdir gupnp-vala-1.0
/usr/lib

is wrong on 64-bit platforms.

> libdir=${exec_prefix}/lib

Ought to be: libdir=${exec_prefix}/lib64

It's a minor error only because ${libdir} is not reused anywhere in that file, for example there is no "Libs:" definition.

Looking at the other gupnp packages it looks to be an issue with them all. I've reported it upstream so they can fix it properly there.

this has been fixed upstream and there should be an official release shortly with the fix.

This bug appears to have been reported against 'rawhide' during the Fedora 11 development cycle.
Changing version to '11'.

More information and reason for this action is here:
http://fedoraproject.org/wiki/BugZappers/HouseKeeping

gupnp-vala-0.5.4-2.fc11 has been submitted as an update for Fedora 11.
http://admin.fedoraproject.org/updates/gupnp-vala-0.5.4-2.fc11

gupnp-vala-0.5.4-2.fc11 has been pushed to the Fedora 11 testing repository.  If problems still persist, please make note of it in this bug report.
 If you want to test the update, you can install it with 
 su -c 'yum --enablerepo=updates-testing update gupnp-vala'.  You can provide feedback for this update here: http://admin.fedoraproject.org/updates/F11/FEDORA-2009-6879

gupnp-vala-0.5.4-2.fc11 has been pushed to the Fedora 11 stable repository.  If problems still persist, please make note of it in this bug report.