LLVM IR linking warning due to mismatching datalayout

[maleadt]

Since #444 we're using a different datalayout, causing:

warning: Linking two modules of different data layouts: '' is 'e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v16:16:16-v32:32:32-v64:64:64-v128:128:128-n16:32:64-ni:10:11:12:13' whereas 'text' is 'e-p:64:64:64:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v16:16:16-v32:32:32-v64:64:64-v128:128:128-n16:32:64-ni:10:11:12:13'

We should probably override the libdevice datalayout to prevent such warnings.

cc @simonbyrne

[maleadt]

Hmm, we're already doing this: https://github.com/JuliaGPU/CUDA.jl/blob/d3b13631f8c608470b11804e07d021735449012c/src/device/runtime.jl#L93-L95

Since the mismatch above is clearly from #444, I'm going to guess that this is due to a wrongly cached compiler runtime. Not sure how though, as updating GPUCompiler should have invalidated CUDA.jl which in turn should have invalidated the cached compiler runtime.

@simonbyrne If this happens again, please investigate and post some additional details so that we can fix this.