fix(pkg-config): Update includedir and libdir to use full installation paths

fixes builds on nix

Author: AhmedAmrNabil

dbc.pc.in

@@ -1,7 +1,7 @@
 prefix=@CMAKE_INSTALL_PREFIX@
 exec_prefix=${prefix}
-includedir=${prefix}/@CMAKE_INSTALL_INCLUDEDIR@
-libdir=${exec_prefix}/@CMAKE_INSTALL_LIBDIR@
+includedir=@CMAKE_INSTALL_FULL_INCLUDEDIR@
+libdir=@CMAKE_INSTALL_FULL_LIBDIR@
 
 Name: @PROJECT_NAME@
 Description: @CPACK_PACKAGE_DESCRIPTION_SUMMARY@