pkgconfig: Fix support for absolute lib and include dirs
pkgconfig: Fix support for absolute lib and include dirs

Using GNUInstallDirs to always have an absolute path regardless of the
user input: https://cmake.org/cmake/help/latest/module/GNUInstallDirs.html

EasyRPG/liblcf,Ghabry/easyrpg-liblcf,Ghabry/easyrpg-liblcf,EasyRPG/liblcf,Ghabry/easyrpg-liblcf,carstene1ns/easyrpg-liblcf,carstene1ns/easyrpg-liblcf,carstene1ns/easyrpg-liblcf,Ghabry/easyrpg-liblcf,EasyRPG/liblcf,EasyRPG/liblcf