cuda_test missing alwayslink

[skyw]

For the reason discussed in #20

_cuda_library inside cuda_test macro needs alwayslink=True. I don't know if there are side effects to set it by default. So filed an issue instead of a PR to add a line.

[cloudhan]

Reasonable, along with cuda_binary.

But that somehow creates implication on the hidden target, will there be some harmful case if we always set alwayslink=True.

Or should we add it implicitly on the hidden target or explicitly on the macro so that to avoid of macro copy pasting in some edge cases?

[skyw]

I would prefer "implicitly on the hidden target" if we can do it safely. Otherwise, exposing it to the macro would do it.
Currently some work around is needed one way or another.