>=sys-fs/device-mapper-1.02.05 has support for pkg-config and generates *.pc files during compiletime, but to acctually install the *.pc files you need to pass --enable-pkgconfig to the configure script, which gentoo currently does not. Please do. Unless you do have a good reason behind not installing them of course.:-)
Created attachment 163361 [details, diff] A patch for a ebuild against your ebuild. As you may see in the patch I have slightly changed some other behaviors to allow for a correct installation, but it seems to install the libs into the right place while allowing to install *.pc into /usr/lib/pkgconfig (and not into /lib/pkgconfig as the mv statement did).
well picked up Xake. thanks for the patch.
fixed in 1.02.27, thanks http://sources.gentoo.org/sys-fs/device-mapper/device-mapper-1.02.27.ebuild?r1=1.1&r2=1.2