Fix the determination of top_builddir
Fix the determination of top_builddir

g_path_get_basename() was used not g_path_get_dirname(); not sure how
this passed my earlier testing.

djdeath/gjs,joeshaw/gjs,djdeath/gjs,joeshaw/gjs,magcius/gjs,endlessm/gjs,magcius/gjs,mtwebster/cjs,mtwebster/cjs,endlessm/gjs,mtwebster/cjs,magcius/gjs,joeshaw/gjs,mtwebster/cjs,joeshaw/gjs,magcius/gjs,pixunil/cjs,djdeath/gjs,pixunil/cjs,pixunil/cjs,djdeath/gjs,mtwebster/cjs,pixunil/cjs,endlessm/gjs,endlessm/gjs,djdeath/gjs,magcius/gjs,joeshaw/gjs,endlessm/gjs,pixunil/cjs