[llvm] [SelectionDAG][Test] Temporarily disable test on Darwin (PR #173836)

[Matt Arsenault via llvm-commits]

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@@ -1,4 +1,5 @@
 ; RUN: llc -O3 < %s
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arsenm wrote:

This should also check the output, and shouldn't need -O3 

https://github.com/llvm/llvm-project/pull/173836