Fix add_test() usage so ctest finds test exes
Fix add_test() usage so ctest finds test exes

Update add_test() usage for new location of executable targets in build
tree.

JoshChristie/displaz,JoshChristie/displaz,JoshChristie/displaz,rotorliu/displaz,rotorliu/displaz,JoshChristie/displaz,rotorliu/displaz,rotorliu/displaz,JoshChristie/displaz