vita.cmake: Giva the same name as custom_command
vita.cmake: Giva the same name as custom_command

this patch would recover the broken name since #120

this patch will print the warning about `circular dependency dropped`
but would work properly.

actually, we should give the right name to target (#129 still has wrong name)

follow the 2011 cmake newgroup thread & cmake issue
- https://cmake.org/pipermail/cmake/2011-March/043375.html
- https://gitlab.kitware.com/cmake/cmake/issues/18627

endrift/vita-toolchain,vitasdk/vita-toolchain,vitasdk/vita-toolchain,endrift/vita-toolchain