switch to using defined globals

[simonbyrne]

Supersedes #1809, requires

• [CUDA_Driver] define libcuda as nothing JuliaPackaging/Yggdrasil#6449
• [CUDA_Runtime] update platform augmentation JuliaPackaging/Yggdrasil#6451
• define all globals CUDA_Runtime_Discovery.jl#2

See #1809 (comment)

[maleadt]

@simonbyrne do you have a way to verify if this works for you?

[simonbyrne]

It works!

The only downside is that it leaves CUDA.libcuda undefined if CUDA_Driver_jll.libcuda == nothing. Would it perhaps be simpler to just import CUDA_Driver_jll: libcuda and leave it at that?

[maleadt]

The only downside is that it leaves CUDA.libcuda undefined if CUDA_Driver_jll.libcuda == nothing. Would it perhaps be simpler to just import CUDA_Driver_jll: libcuda and leave it at that?

That won't work: CUDA_Driver_jll isn't available on all platforms, so its init block doesn't always run (JuliaPackaging/JLLWrappers.jl#50). That's why CUDA.jl falls back to a simple Libdl.find_library search and uses that to set CUDA.libcuda. If we'd import CUDA_Driver_jll: libcuda, we can't redefine it in case it is nothing.