qt 4.8.x installs pkgconfig file with {moc,uic,rcc}_location pointing to build dir

4.8.x (I have qt-core-4.8.2 under Gentoo) creates the pkg-config info using the build dir instead of the install dir, so when building some other package (kernel make xconfig for example) that depends on qt, it fails to find some moc stuff. Sorry for the sloppy wording - I've already fixed it, so I no longer have the exact error message, but it was a file not found for some moc component. I used the patch from the Gentoo bug: https://bugs.gentoo.org/show_bug.cgi?id=401025, which also has a better description of the problem. I've attached that patch, since its author is not certain if it's the right way to fix the problem, which appears to be related to the build directory path (PORTAGE_TMPDIR under Gentoo) starting with /usr.