Fix incorrect paths in .pc files.

The change in 67c3878ef10449b241c37d1022e2518029860335 used the
CMAKE_INSTALL_x variables instead of CMAKE_INSTALL_FULL_x; the former
contain things like "include" instead of full paths, so the resulting
.pc files break packages that depend on poppler. Use the latter.

Also fix a missing @ in the qt5 file.

Bug #103578
7 files changed