A litte late, obviously, but I thought I'd share the results of what I just found:
On 64-bit Fedora, you need to put the line below in your .bashrc (or, rather, the root user's .bashrc, because you need to install as root):
export PKG_CONFIG_PATH=$PKG_CONFIG_PATH:/usr/lib/pkgconfig
This is because, as discussed on IRC, Fedora uses /usr/lib64 for 64-bit applications.