[llvm] [CI] monolithic-linux improvements (PR #135499)

[Aiden Grossman via llvm-commits]

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@@ -28,10 +27,14 @@ if [[ -n "${CLEAR_CACHE:-}" ]]; then
   ccache --clear
 fi
 
+mkdir -p artifacts/reproducers
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boomanaiden154 wrote:

Note that this will not end up being uploaded on the Github side, although I should probably set something up to get that working.

https://github.com/llvm/llvm-project/pull/135499