qtAddModule() skips adding standard library paths to LIBS. however, as
processPrlFiles() didn't know anything about that, it would not find the
prl files of qt libraries in these paths.
so centralize the definition of these default paths (we should actually
ask the linker for them) and use it in both places.
do the same for the include paths for symmetry.
Change-Id: I7e3692dc2d1c2d0c97a9151d15887b1263de137a
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>