Fixes bugs in create_pkgconfig_file cmake macro
Fixes bugs in create_pkgconfig_file cmake macro

Bugs introduced by commit 5a3027c93eb5f234537d0d58cc87df2fa80f5f3a
${prefix} was missing in ${libdir} and ${includedir} variables.
${CMAKE_INSTALL_LIBDIR} and ${CMAKE_INSTALL_INCLUDEDIR} cannot be escaped
in order to be substituted by their values.

Signed-off-by: Luís Pereira <95d1463b1ff9eef535e39fb0d755bc242cfcea61@gmail.com>

DrTobe/libqtxdg,lxde/libqtxdg,gilir/libqtxdg-qt5,libqtxdg/libqtxdg,DrTobe/libqtxdg,luis-pereira/libqtxdg,libqtxdg/libqtxdg,DrTobe/libqtxdg,gilir/libqtxdg-qt5,lxde/libqtxdg,luis-pereira/libqtxdg